violently projected upward they revert or fall down again by reason of the magnetique Attraction of the Earth and it now remains onely that we consider the Reasons of that other species of motion Reflex or Rebounding whereby Bodies being also violently moved or projected any way are impeded in their course and Diverted from the line of their Direction by other bodies encountring them Concerning this Theorem therefore be pleased to know that among all Reflexions by way of Rebound or Resilition that is the Chiefest when a body projected and impinged against another body is returned from thence directly or in the same line toward the place from whence it was projected which always happens when the Projection is made to right Angles or in regular line such as that in which a Heavy body descends upon an horizontal plane And all other Reflections are in dignity inferior thereunto as such whereby the thing projected doth not rebound in a direct line toward the same point from whence it was projected but to some other region by other lines according as it is projected in lines more or less oblique Because with what inclination a body falls upon a plane with the very same inclination doth it rebound from the plane especially a Globe and such as is of an uniform matter and consequently hath the Centre of magnitude and that of Gravity coincident in the same point so that by how much the more oblique the projection is and how much the less is the Angle made of its line with the line of the plane called the Angle of Incidence so much the more oblique is the reflexion made and so much the less the Angle made of its line with the line of the plane continued called the Angle of Reflexion and that so long as till the line of projection shall become parallel to the plane and so no body occurring to or encountring the projectum no reflexion at all be made Know moreover that betwixt No Reflexion at all and the Least Reflexion that is possible there may be assigned as it were a certain Medium and that is the Emersion or Rising up again of a weight appensed to a thread or Lutestring when performing a vibration or swing from one side to the other it ascends from the perpendicular Line to which by descending it had reduced it self For in that case no â—â—â—lecting body doth occur a simple Arch is described and yâ—â—â—here is as a certain Procidence or falling down to the lowest point of the Arch so also a certain Resilition or rising up again from â—he lowest point of the Arch toward the contrary side Again having conceived a direct line touching the lowest point of the Arch so as that the weight suspended by a string may in its vibration glance upon it with its lowest extreme and onely in a point touch the horizontal line you shall have on each side an Angle madâ— from the Arch and the line touching it which is therefore called the Angle of Contingence and because Geometricians demonstrateâ— that the Angle of Contingence which truly differs from a right line is less than any Rectilinear Angle however acute therefore may each of those Angles be said to be Median betwixt the right line and the Angle either of Incidenceâ— or of Reflexion how small soever it be and consequently the Emersion of the weight in Vibration may as justly be said to be Median betwixt the smallest Reflexion and none at all However this Emersion seems to 〈◊〉 the Rule of all Reflection whatever for as in the Vibration of a weight appensed to a string and describing a simple Arch the Aâ—gle of its Emersion is always equal to the Angle of its Procidenâ—â— so in Projection describing an Angular line the Angle of Reflection is always quantum ex se est equal to the Angle of Incidence We say quantum ex se est for otherwise whether it be sensible or not because so long as the Projectum is transferred it is aâ—ways somewhat depressed toward the earth for the reason formerly alleadged thence comes it that the Reflexion can neither be so strong or smart as the Incidence nor make as great an angle 〈◊〉 arise to as great an altitude Which we insinuate that we might not insist upon this advertisement that the Aequality of the Angle of the Reflexion to that of the Incidence may be so much thâ— less by how much the less the projected body comes to a spherical figure or doth consist of matter the less uniform For to attain to that Aequality of the Angels of Incidence and Reflexion necessary it is that the body projected be exactly spherical and of Uniâ—orm matter and so having the Centre of Gravity and the Centre of magnitude coincident in one and the same point as we have formerly intimated it being as well against Reason as Experience that bodies wanting those conditions should arise to that aequaliâ—â— which that we may the better understanâ— let us consider that 〈◊〉 in a Globe or Ball Falling down we regard onely that Gravity which it acquires in its descent from the magnetique Attraction of the Earth so in a Globe or Ball Projected we are to regard onely that Impetus or Force which being imprest upon it by the Projicient supplies the place of Gravity and in respect whereof the Centre of its Gravity may be conceived to be one with that of its magnitude Let a Ball therefore be projected Directly or to right Angles upon a plane and because in that case that Fibre must be the Axis of its Gravity whose extreme going foremost is impinged against the plane thence is it manifest that the Repression must be made in a direct line along that Axis the parallel Fibres in equal number on each part invironing that Axis and so not swaying or diverting the ball more to one part than to another by reason of any the least disproportion of quantity on either side Then lâ—t the same Ball be projected Obliquely against the same plane and because in this case not that middle Fibre which constituteth the Axis of Gravity but some one or other of the Fibres circumstant about it must with one of its extreams strike against the plane therefore is it necessary that that same Fibre be repressed by that impulse and by that repression compelled to give backward toward its contrary extream and thereby in some measure to oppose the motion begun which it wholly overcome and so the ball would rebound from the plane the same way it came if the Fibres on that side the Axis of Gravity which is neerest to the plane were equal in number to that are on the farther or contrary side of it but because those Fibres that are on the farther side or on the part of the Centre and Axis are far more in number and so theâ—e is a greater quantity of matter and consequently a greater force imprest than on the side neerer to the plane
therefore doth the begun motion persever as praevailing upon the repression and renitency of the Fibre impinged against the plane and since it cannot be continued in a direct line because of the impediment ariseing from the parts cohaerent it is continued by that way it can i. e. by the open and free obliquity of the plane But this of necessity must be done with some certain Evolution of the Ball and with the contact of the Fibres posited in order both toward the Axis and beyond it and while this is in doing every Fibre strives to give back but because the farther part doth yet praevail over the neerer therefore doth the neerer part still follow the sway and conform to the inclination and conduct of the farther and all the toucht Fibres change their situation nor are they any longer capable of returning by the same way they came because they no longer respect that part from whence they came We say with the Contact of the plane by the Fibres posited toward the Axis and beyond it because since in that Evolution or Turn of the Ball the extream of the Axis toucheth the plane yet nevertheless no Resilition or Rebound is therefore caused in that instant and if there were a resilition at that time it would be to a perpendicular as well the Axis as all the circumstant Fibres being erected perpendicularly upon the face of the plane but the Resilition there must be beyond it because the force of the farther part of the Fibres doth yet praevail over that of the neerer For the Force of the farther part doth yet continue direct and intire but that of the neerer is reflected and by the repression somewhat debilitated and therefore the Resilition cannot be made until so much of Repression and Debilitation be made in the further part as was made at first in the neerer And that must of necessity be done so soon as ever the plane is touched by some one Fibre which is distant from the Axis as much beyond as that Fibre which first touched the plane is distant from the Axis on this side for then do the two forces become equal and so one part of the Fibres having no reason any longer to praevail over the other by counter inclination the Ball instantly ceaseth to touch the plane and flies off from it toward that region to which the Axis and all the circumstant Fibres are then i. e. after the Evolution directed Now because the Ball is after this manner reflected from the plane with the same inclination or obliquity with which it was impinged against it it is an evident consequence that the Angle of its Reflexion must be commensurable by the Angle of its Incidence and that each of them must be so much the more Obtuse by how much less the line of projection doth recede from a perpendicular and contrariwise so much the more Acute by how much more the line of projection doth recede from a perpendicular or how much neerer it approacheth to a parallel with the plane From these Considerations we may infer Two Observables The One that the oblique projection of a Globe against a plane is composed of a double Parallel the one with the Perpendicular the other with the plane for the Globe at one and the same time tends both to the plane and to that part toward which the plane runs out forward The Other that Nature loseth nothing of her right by the Reflexion of bodies forasmuch as she may nevertheless be allowed still to affect and pursue the shortest or neerest way for because the Angle of Reflexion above the plane is equal to that Angle which would have been below the plane in case the plane had not hinderd the progress of the line of projection beyond it by reason of the Angles Equal at the Vertex as Geometricians speak therefore is the Reflex way equal to the Direct and consequently to the shortest in which the ball projected could have tended from this to that place Here to bring up the rear of this Section we might advance a discourse concerning the Aptitude and Ineptitude of Bodies to Reflexion but the dulness of our Pen with long writing as well as the Confidence we have of our Readers Collective Abilities inclining us to all possible brevity we judge it sufficient onely to advertise that what we have formerly said concerning the Aptitude and Ineptitude of Bodies to Projection hath anticipated that Disquisition For certain it is in the General that such Bodies which are More Compact Cohaerent and Hard as they may be with more vehemence and to greater distance Projected so may they with more vehemence and to greater distance Rebound or be Reflected provided they be impinged against other bodies of requisite Compactness Cohaerence and Hardness And the Reason why a Tennis-ball doth make a far greater Rebound than a Globe of Brass of the same magnitude and thrown with equal force is onely this that there is not a proportion betwixt the Force imprest by the Projicient and the Gravity of each of them or betwixt the Gravity of each and the Resistence of the Plane Which holds true also concerning other bodies of different Contextures CONCLUSION Ingenious Reader I Have kept you long at Sea I confess and such was the Unskilfulness of my Pen though steered for the most part according to the lines drawn on those excellent Charts of Epicurus and Gassendus often shipwrackt your Patience But be pleased to consider that our way was very Long and taedious insomuch as we had no less than the whole of that vast and deep Ocean of Sublunary Corporeal Natures to sayl over that our passage was full of Difficulties as well in respect of those sundry Rocks of Incertitude which the great Obscurity of most of those Arguments whose discovery we attempted inevitably cast us upon as of those frequent Mists and Foggs which the exceeding Variety of mens Opinions concerning them surrounded and almost benighted our judgement withal and chiefly that if by the voyage your Understanding is brought home not only safe but inriched though in the least measure with that inestimable Wealth the Knowledge of Truth or what is so Like to Truth as to satisfie your Curiosity as fully as I have reason to congratulate my self for the happiness of my Care and Industry in being your Pilot so must you to esteem the adventure of your Time and Attention compensated with good Advantage And now you are on Land agen give me leave at parting to tell you That all the Fare I shall ever demand of you is only a Candid sentiment of my Good-will and cordial Devotion to the Commonwealth of Philosophy Which indeed doth so strongly Animate me on to enterprizes of Publique Utility though but to those in the Second Form of Scholars that I can be well contented not only to neglect opportunities of Temporal advantages to my self while I am imployed in the study how to contribute to the
to their Exhalation Thus is Water much sooner evaporated then Oyl and Lead then Silver 3 Anti-Atomist If Atoms be unequal in their superfice and have angular and hamous processes then are they capable of having their rugosities planed by detrition and their hooks and points taken off by amputation contrary to their principle propriety Indivisibility Atomist the hooks angles asperities and processes of Atoms are as insecable and infrangible as the residue of their bodies in respect an equal solidity belongs to them by reason of their defect of Inanity interspersed the intermixture of Inanity being the Cause of all Divisibility Haec quae sunt rerum primordia nulla potest vis Stringere nam solido vincunt ea corpore demum 4 Anti-Atomist That Bodies of small circumscription such as grains of sand may be amassed from a syndrome and coagmentation of Atoms seems indeed to stand in some proportion to probability but to conceive a possibility that so vast a Bulk as the adspectable World bears may arise out of things but one degree above nothing such insensible materials convened and conglobated is a symptome of such madness as Melancholy adust cannot excuse and for which Physitians are yet to study a cure Atomist To doubt the possibility nay dispute the probability of it is certainly the greater madness For since a small stone may be made up of a Coagmentation of grains of Sand a multitude of small stones by coacervation make up a Rock many Rocks by aggregation make a Mountain many Mountains by coaptation make up the Globe of Earth since the Sun the Heavens nay the World may arise from the conjunction of parts of dimensions equal to the Terrestrial Globe what impossibility doth he incurr who conceives the Universe to be amassed out of Atoms Doubtless no Bulk can be imagined of such immense Dimensions as that the greatest parts thereof may not be divided into less and those again be subdivided into less so that by a successive degradation down the scale of Magnitude we may not at last arrive at the foot thereof which cannot be conceived other then Atoms Should it appear unconceivable to any that a Pismire may perform a perambulation round the terrestrial Globe we advise him to institute this Climax of Dimensions and consider first that the ambite of the Earth is defined by miles that miles are commensurated by paces paces consist of feet feet of digits digits of grains c. and then He may soon be convinced that the step of a Pismire holds no great disproportion to a grain and that a grain holds a manifest proportion to a digit a digit to a foot a foot to a pace a pace to a perch a perch to a furlong a furlong to a mile and so to the circumference of the whole Earth yea by multiplication to the convexity of the whole World If any expect a further illustration of this point it can cost him no more but the pains of reading the 45. page of our Treatise against Atheism and of Archimeds book de Arenarum Numero 5 Anti-Atomist If all peices of Nature derived their origine from Individual Particles then would there be no need of Seminalities to specifie each production but every thing would arise indiscriminately from Atoms accidentally concurring and cohaering so that Vegetables might spring up without the praeactivity of seeds without the assistance of moysture without the fructifying influence of the Sun without the nutrication of the Earth and all Animals be generated spontaneously or without the prolification of distinct sexes Atomist This inference is ingenuine because unnecessary since all Atoms are not Consimilar or of one sort nor have they an equal aptitude to the Conformation of all Bodies Hence comes it that of them are first composed certain Moleculae small masses of various figures which are the seminaries of various productions and then from those determinate seminaries do all specifical Generations receive their contexture and Constitution so praecisely that they cannot owe their Configuration to any others And therefore since the Earth impraegnated with Fertility by the sacred Magick of the Creators Benediction contains the seeds of all Vegetables they cannot arise but from the Earth nor subsist or augment without roots by the mediation of which other small consimilar Masses of Atoms are continually allected for their nutrition nor without moysture by the benefit of which those minute masses are diluted and so adapted for transportation and final assimilation nor without the influence of the Sun by vertue whereof their vegetative Faculty is conserved cherished and promoted in its operations Which Reason is aequivalent also to the Generation Nutrition and Increment of Animals 6 Anti-Atomist If your Proto-Element Atoms be the Principle of our 4 common Elements according to the various Configurations of it into Moleculae or small masses and that those are the Seminaries of all things then may it be thence inferred that the Seeds of Fire are invisibly contained in Flints nay more in a Sphaerical Glass of Water exposed to the directly incident rayes of the Sun our sense convincing that Fire is usually kindled either way Atomist Allowing the legality of your Illation we affirm that in a Flint are concealed not only the Atoms but Moleculae or Seeds of Fire which wanting only retection or liberty of Exsilition to their apparence in the forme of fire acquire it by excussion and pursuing their own rapid motion undiquaque discover themselves both by affecting the sight and accension of any easily combustible matter on which they shall pitch and into whose pores they shall with exceeding Celerity penetrate Nor can any man solve this eminent Phaenomenon so well as by conceiving that the body of a Flint being composed of many igneous i. e. most exile sphaerical and agile Atoms wedged in among others of different dimensions and figures which contexture is the Cause of its Hardness Rigidity and Friability upon percussion by some other body conveniently hard the insensible Particles thereof suffering extraordinary stress and violence in regard it hath but little and few Vacuola or empty spaces intermixt and so wanting room to recede and disperse are conglomorated and agitated among themselves with such impetuositie as determinately causeth the constitution of Fire It being manifest that violent motion generateth Heat and confessed even by Aristotle 1. Meteor 3. that Fire is nothing but the Hyperbole or last degree of Heat Secondly That the seeds of Fire are not contained either in the sphaerical Glass or the the Water included therein but in the Beams of the Sun whose Composition is altogether of Igneous Atoms which being deradiated in dispersed lines want only Concurse and Coition to their investment in the visible form of Fire and that the Figure of the Glass naturally induceth it being the nature of either a Convex or Concave Glass to transmit many Beams variously incident towards one and the same point which the virtue of Union advanceth to the force of
Instance in the Visible species of the Foot of a Handworm ibid. 14 By exemplifying in the numerous round Films of Wax successively derepted from a Wax tapor by the flame thereof in the space of an hour and 142 15 In the innumerable Films of Oyl likewise successively delibrated by the flame of an Ellychnium or Match perpendicularly floating in a vessel of equal capacity with Solomons Brazen Sea in the space of 48 hours ibid. 16 By the Analogy betwixt an Odorable and Visible Species ibid. 17 The Manner and Reason of the Production of visible Images according to the hypothesis of Epicurus 143 18 The Celerity of the Motion of visible Images reasoned and compared to that of the Light of the Sun 144 19 The Translation of a moveable from place to place in an indivisible point of time impossible and why ibid. 20 The Facility of the Abduction or Avolation of Images Visible from solid Concretions solved by the Spontaneous Exsilition of their superficial Atoms and the Sollicitation of Light incident upon them ibid. 21 That Objects do not emit their Visible Images but when Illustrated a Conceit though paradoxical yet not improbable 145 SECT II. ARTIC 1 VIsible Images Systatical described and distinguisht from Apostatical ones 146 2 Their Existence assured by the testimony of Diodorus Siculus and ibid. 3 Damascius together with the Autopsy of Kircher ibid. 4 Kirchers Description of that famous Apparition at Rhegium called Morgana Rheginorum and 147 5 Most ingenious Investigation of the Causes thereof ibid. 6 His admirable Artifice for the exhibition of the like aereal Representation in Imitation of Nature 148 CHAP. III. Concerning the Manner and Reason of VISION p. 149. SECT I. ARTIC 1 THe Reason of Vision according to the opinion of the Stoicks 149 2 Of Aristotle 150 3 Of the Pythagoreans ibid. 4 Of Empedocles ibid. 5 Of Plato ibid. 6 Of Epicurus ibid. 7 Of Mons. Des Chartes 151 8 The ingenuity of Des Chartes Conceit acknowledged but the solidity indubitated 152 9 The Opinion of Epicurus more satisfactory then any other because more Rational and less obnoxious to inexplicable Difficulties ibid. 10 The Two most considerable Difficulties opposed to Epicurus position of the Incursion of Substantial Images into the Eye 153 SECT II. ARTIC 1 THat the superfice of no body is perfectly smooth evicted by solid Reason and Autopsie ibid. 2 That the visible Image doth consist of so many Rays as there are points designable in the whole superfice of the object and that each Ray hath its line of Tendency direct respective to the face of that particle in the superfice from which it is emitted 154 3 That the Density and Union of the Rays composing the visible Image is greater or less according to their less or greater Elongation from the Object ibid. 4 That the Visible Image is neither total in the total medium nor total in every part thereof but so manifold as are the parts of the medium from which the object is discernable Contrary to the Aristoteleans 155 5 PARADOX That no man can see the same particle of an object with both Eys at once nay not with the same Eye if the level of its Visive Axe be changed ibid. 6 CONSECTARY That the Medium is not possessed with one simple Image but by an Aggregate of innumerable Images deradiate from the same object all which notwithstanding constitute but one entire Image 156 7 CONSECTARY 2. That Myriads of different Images emanant from different objects may be Coexistent in the Aer without reciprocal penetration of Dimensions or Confusion of particles contrary to the Peripateticks ibid 8 That the place of the visible Images ultimate Reception and complete Perception is the Concave of the Retina Tunica 157 9 That the Faculty forms a judgement of the Conditions of the Object according to the representation thereof by the Image at its impression on the principal part of Vision the Amphiblestroides ibid. 10 CONSECTARY That the Image is the Cause of the Objects apparence of this or that determinate Magnitude 158 11 CONSECTARY 2 That no Image can replenish the Concave of the Retina Tunica unless it be deradiated from an object of an almost Hemispherical ambite 159 12 Why when the Eye is open there is alwayes pourtrayed in the bottom thereof some one Total Image whose various Parts are the Special Images of the several things included in the visual Hemisphere ibid. 13 PARADOX That the prospect of a shilling or object of a small diametre is as great as the Prospect of the Firmament 160 14 Why an object appears both greater in Dimensions and more Distinct in parts neer at hand than far off ibid. 15 Why an object speculated through a Convex Lens appears both greater and more distinct but through a Concave less and more Confused than when speculated only with the Eye 161 16 DIGRESSION What Figur'd Perspicils are convenient for Old and what for Purblind persons 162 17 That to the Dijudication of one of two objects apparently Equal to be really the Greater is not required a greater Image but only an Opinion of its greater Distance 163 18 Des Cartes Opinion concerning the Reason of the Sights apprehending the Distance of an object 164 19 Vnsatisfactory and that for two considerations ibid. 20 And that more solidone of Gassendus viz. that the Cause of our apprehending the Distance of an object consisteth in the Comparation of the several things interjacent betwixt the object and the Eye by the Rational Faculty embraced and corroborated ibid. 21 PARADOX That the same Object speculated by the same man at the same distance and in the same degree of light doth alwayes appear greater to one Eye than the other 165 22 A second PARADOX That all men see distinctly but with one Eye at once contrary to that eminent Optical Axiom that the Visive Axes of both eyâ— concur and unite in the object 166 23 The three degrees of Vision viz. most perfect perfect and imperfect and the verity of the Paradox restrained onely to the two former Degrees 167 SECT III. ARTIC 1 A Research into the Reason of the different Effects of Convex and Concave Glasses as well Dioptrical as Catoptrical ibid. 2 A COROLLARIE Hinting the Causes why an Elliptical Concave reflects the incident rays in a more Acute angle than a Parabolical and a Parabolical than a Spherical 170 3 A CONSECTARY Why a Plane Perspicil exhibits an object in genuine Dimensions but a Convex in Amplified and a Concave in minorated 171 SECT IV. ARTIC 1 A Recapitulation of the principal Arguments precedent and summary of the subsequent 173 2 The Eye Anatomized and the proper use of each Part thereof either absolutely Necessary or onely Advantagious to Vision concisely demonstrated viz. 1 The Diaphanity of the Horny Membrane and the three Humors Aqueous Chrystalline and Vitreous 2 The Convexity of all its parts except the Amphiblestroides 3 The Uvea Tunica and Iris. 4 The Pupilla 5 The Blackness
of the inside of the Uvea Tunica 6 The Tunica Arachnoides 7 The Ciliary Filaments thereof 8 The Chrystalline 9 The Retina Tunica 10 The six Muscles viz. 1 The Direct as the Atollent Depriment Adducent Abducent 2 And Oblique as the 2 Circumactors or Lovers Muscles 173 to 177 3 Why the Situation of an object is perceived by the sight 177 4 The Reason of the eversion of the Image in the Amphiblestroides 178 5 The same illustrate by an Experiment ibid. 6 Why the Motion and Quiet of objects are discerned by the sight ibid. 7 Why Catoptrical Images imitate the motions of their Antitipes or Originals ibid. 8 Why the right side of a Catoptrical Image respects the Left of its Exemplar And why two Catoptrick Glasses confrontingly posited cause a Restitution of the parts of the Image to the natural Form 180 CHAP. IV. The Nature of Colours p. 182. SECT I. ARTIC 1 THe Argument duly acknowledged to be superlatively Difficult if not absolutely Acataleptical ibid. 2 The sentence of Aristotle concerning the Nature of Colours and the Commentary of Scaliger thereupon 183 3 The opinion of Plato ibid. 4 Of the Pythagorean and Stoick 184 5 Of the Spagyrical Philosophers ibid. 6 The reason of the Authors desertion of all these and election of Democritus and Epicurus judgement touching the Generation of Colours ibid. 7 The Text of Epicurus fully and faithfully expounded 185 SECT II. ARTIC 1 A PARADOX That there are no Colours in the Dark 186 2 A familiar Experiment attesting the Verity thereof ibid. 3 The Constancy of all Artificial Tinctures dependent on the constancy of Disposition in the superficial Particles of the Bodies that wear them 187 4 That so generally magnified Distinction of Colours into Inhaerent and meerly Apparent redargued of manifest Contradiction ibid. 5 The Emphatical or Evanid Colours created by Prisms no less Real and Inhaerent than the most Durable Tinctures 188 6 COROLLARY The Reasons of Emphatical Colours appinged on Bodies objected by a Prism 189 7 The true Difference of Emphatical and Durable Colours briefly stated ibid. 8 No Colour Formally inhaerent in objects but only Materially or Effectively contrary to the constant Tenent of the Schools ibid 9 The same farther vindicated from Difficulty by the tempestive Recognition of some praecedent Assumptions of the Atomists 190 SECT III. ARTIC 1 THe Nativity of White or the reason of its perception by the sight 191 2 Black a meer Privation of Light ibid. 3 The Genealogy of all Intermediate Colors ibid. 4 The Causes of the Sympathy and Antipathy of some Colours 192 5 The intermisâ—ion of small shadows among the lines of Light absolutely necessary to the Generation of any Intermediate Colour ibid. 6 Two eminent PROBLEMS concerning the Generation and Transposition of the Vermillion and Caerule appinged on Bodies by Prismes 193 7 The Solution of the Former with a rational Conjecture of the Cause of the Blew apparent in the Concave of the Heavens 194 8 The Solution of the Latter 195 9 The Reasons why the Author proceeds not to investigate the Causes of Compound Colours in Particular 196 10 He confesseth the Erection of this whole Discourse on simple Conjecture and enumerates the Difficulties to be subdued by him who hopes to attain an Apodictical Knowledge of the Essence and Causes of Colours ibid. 11 Des Cartes attempt to dissolve the chief of those Difficulties unsuccessful because grounded on an unstable Hypothesis 197 CHAP. V. The Nature of Light p. 198. SECT I. ARTIC 1 THe Clasp or Ligament of this to the praecedent Chapter ibid. 2 The Authors Notion of the Rays of Light ibid. 3 A Parallelism betwixt a stream of Water exsilient from the Cock of a Cistern and a Ray of Light emanent from its Lucid Fountain ibid PRAECONSIDERABLES 199 4 Light distinguisht into Primary Secondary c. 199 5 All Light Debilitated by Reflection and why ibid. 6 An Example sensibly demomonstrating the same 200 7 That light is in perpetual Motion according to Aristotle ibid. 8 Light why Corroborated in some cases and Debilitated in others by Refraction 201 COROLLARY Why the Figure of the Sun both rising and setting appears rather Elliptical than Sphaerical ibid. 9 PARADOX That the proportion of Solary Rays reflected by the superior Aer or Aether toward the Earth is so small as not to be sensible 202 10 That every Lucid Body as Lucid doth emit its Rays Sphaerically but as Visible Pyramidally ibid. 11 That Light is invisible in the pure medium 203 SECT II. ARTIC 1 THe necessity of the Authors confirmation of the First Praeconsiderable 204 2 The Corporiety of Light demonstrated by its just Attributes viz. 1 Locomotion 2 Resilition 3 Refraction 4 Coition 5 Disgregation 6 Igniety 224 225 3 Aristotles Definition of Light a meer Ambage and incomprehensible 205 4 TheCorporiety of Light imports not the Coexistence of two Bodies in one Place contrary to the Peripatetick 206 5 Nor the motion of a Body to be Instantaneous ibid. 6 The Invisibility of Light in the limpid medium no Argument of its Immateriality as the Peripatetick praesumes ibid. 7 The Corporiety of Light fully consistent with the Duration of the Sun contrary to the Peripatetick 207 8 The insensibility of Heat in many Lucent Bodies no valid Argument against the praesent Thesis that Light is Flame Attenuated ibid. CHAP. VI. The Nature of a Sound p 208. SECT I. ARTIC 1 AN Elogy of the sense of Hearing and the Relation of this and the praecedent Chapter ibid. 2 The great Affinity betwixt Visible and Audible species in their representation of the superficial Conditions of Objects 209 3 In the Causes and manner of their Destruction ibid. 4 In their Actinobolism or Diffusion both Sphaerical and Pyramidal 210 5 In their certifying the sense of the Magnitude Figure and other Qualities of their Originals ibid. 6 In the obscuration of Less by Greater 211 7 In their offence of the organs when excessive ibid. 8 In their production of Heat by Multiplication ibid. 9 In their Variability according to the various disposition of the Medium ibid. 10 In their chief Attributes of Locomotion Exsilition Impaction Resilition Disgregation Congregation ibid. SECT II. ARTIC 1 THe Product of the Praemises concerning the points of Consâ—nt and Dissent of Audible and Visible Species viz That Sounds are Corporeal 213 2 An obstruction of praejudice from the generally supposed repugnant Authorities of some of the Ancients expeded ibid. 3 An Argument of the Corporiety of Sounds 214 4 A Second Argument ibid. COROLLARY ibid. 5 The Causes of Concurrent Echoes where the Audient is equally almost distant from the Sonant and Repercutient ibid. COROLLARY 2. 215 6 Why Concaves yield the strongest and longest Sounds ibid. COROLLARY 3. ibid 7 The reason of Concurrent Echoes where the Audient is neer the 〈◊〉 and remote from the sonant ibid. COROLLARY 4. ibid. 8 Wâ—y 〈◊〉 Monophon rehearse so much the fâ—â—er syllables by how much neerer the audient is
the Constitution of all sorts of things 434 CHAP. II. Of Motion p. 435. SECT I. ARTIC 1 WHy the Nature of Motion which deserved to have been the subject of the first speculation was reserved to be the Argument of the Last in this Physiology ibid. 2 An Epicurean Principle of fundamental concern to motion 436 3 Aristotles Position that the first Principle of motion is the very Forme of the thing moved absolutely incomprehensible unless the Form of a thing be conceived to be a certain tenuious Contexture of most subtile and most active Atoms ibid. 4 A second Epicurean Fundamental concerning motion and the state of the Difference betwixt Epicurus Aristotle and Plato touching the same 4â—7 5 Epicurus's Definition of motion to be the Remove of a body from place to place much more intelligible and proper than Aristotles that it is the Act of an Entity in power as it is such 438 6 Empericus his Objections against that Definition of Epicurus and the full Solution of each 439 7 That there is motion contrary to the Sophisms of Parmenides Melissus Zeno Diodorus and the Scepticks 441 SECT II. ARTIC 1 ARistotles Definitions of Natural and Violent motion incompetent and more adaequate ones substituted in the room of them 444 2 The same deduced from the First Epicurean Principle of motion praemised and three considerable Conclusions extracted from thence 445 3 A short survey of Aristotles whole theory concerning the Natural motion of Inanimates and the Errors thereof 446 4 Uniformity or Aequability the proper Character of a Natural motion and the want of uniformity of a Violent 447 5 The Downward motion of Inanimates derived from an External Principle contrary to Aristotle 449 6 That that External Principle is the Magnetique Attraction of the Earth 450 7 That the Vpward motion of Light things is not Accelerated in every degree of their Ascent as Aristotle praecariously affirmed but the Downward motion of Heavy things is Accelerated in every degree of their Descent ibid 8 The Cause of that Encrease of Velocity in Bodies descending not the Augmentation of their Specifical Perfection as they approach neerer and neerer to their proper place as Simplicius makes Aristotle to have thought 452 9 Nor the Diminution of the quantity of Aer underneath them as some Others conjectured ibid. 10 Nor the Gradual Diminution of the Force imprest upon them in their projection upward as Hipparchus alleadged 453 11 But the Magnetique Attraction of the Earth ibid. 12 That the Proportion or Ration of Celerity to Celerity encreasing in the descent of Heavy things is not the same as the Proportion or Ration of Space to Space which they pervade contrary to Michael Varro the Mathematician 455 13 But that the moments or Equal degrees of Celerity carry the same proportion as the moments or equal degrees of Time during the motion according to the Illustrious Galilaeo 456 14 Galilaeo's Grounds Experience and Reason 457 15 The same Demonstrated 458 16 The Physical Reason of that Proportion 460 17 The Reason of the Equal Velocity of Bodies of very different weights falling from the same altitude inferred from the same Theory ibid. 18 Gravity Distinguish't into Simple and Adjectitious 461 19 The Rate of that superlative velocity with which a Bullet would be carried in case it should fall from the Moon Sun or region of the Fixed stars to the Earth and from each of those vast heights to the Centre of the Earth 462 SECT III. ARTIC 1 WHat and whence is that Force or Virtue Motive whereby Bodies Projected are carried on after their Dismission from the Projicient 463 2 The Mâ—nner of the Impression of that Force 465 3 That all Mâ—tion in a free or Empty space must be Vniform and Perpetual and that the chief Cause of the Inequality and Brevity of the motion of things projected through the Atmosphere is the maâ—netique Attraction of the Earth 466 4 That in the Atmosphere no body can be projected in a Direct line unless perpendicularly Vpward or Downward and why 468 5 That the Motion of a stone projâ—cted upwards obliquely is Composed of an Horizontal and Perpendicular together ibid. 6 Demonstration of that Composition 469 7 That of the two different Forces impressed upon a ball thrown upward from the hand of a man standing in a ship that is under sayl the one doth not destroy the other but each attains its proper scope ibid. 8 That the space of time in which the Ball is Ascending from the Foot to the Top of the Mast is equal to that in which it is again Descending from the top to the foot 470 9 That though the Perpendicular motion of a stone thrown obliquely upward be unequal both in its ascent and descent yet is the Horizontal of Equal Velocity in all parts of space ibid. 10 The Reason and Manner of the Reflexion or Rebounding motion of Bodies diverted from the line of their direction by others encountring them 471 11 That the Emersion of a weight appensed to a string from the perpendicular to which it had reduced it self in Vibration is a Reflexion Median betwixt No Reflexion at all and the Least Reflexion assignable and the Rule of all other Reflexion whatever 472 12 The Reason of the Equality of the Angles of Incidence and Reflexion ibid. 13 Two Inferences from the praemises viz· 1 That the oblique Projection of a Globe against a plane is composed of a double Parallel and 2 That Nature suffers no diminution of her right to the shortest way by Reflexion 474 14 Wherein the Aptitude or Ineptitude of bodies to Reflexion doth consist ibid. BOOK the FIRST CHAP. I. All Modern Philosophers reduced to four general Orders and the principal causes of their Dissention SECT I. IF we look back into the Monuments or Remains of Antiquitie we shall observe as many several SECTS of Philosophers as were the Olympiads in which Greece wore the Imperial Diadem of Letters nay perhaps as many as she contained Academies and publike Professors of Arts and Sciences Each Master affecting to be reputed the principal Secretary of Nature and his Disciples their minds being deeply imbued with his principles admiring him as the Grand Oracle of Divinitie and the infallible Dictator of Scientifical Maxims The chiefest most diffused and most memorable of these Sects were the Pythagorean the Stoick the Platonist the Academick the Peripatetick the Epicurean and what derided all the rest the Pyrrhonian or Sceptick which feircely contended for the Laurel by subtle disputations on the side of absolute Ignorance and aspired to the Monarchy of Wisdom by detecting the vanitie and incertitude of all Natural Science As for the Megarick Eretrick Cyreniack Annicerian Theodorian Cynick Eliack Dialectick and others less famous Diogenes Laertius de vita Philosophor hath preserved not only a faithful Catalogue of them but hath also recorded their originals declinations periods opinions If we enquire into the Modern state of Learning down even to our present
which this eminent Experiment exhibits to observation the least whereof seems to require a second Oedipus more perspicacious then the first for the accommodation thereof though but to plausible and verisimilous Causes and might had Aristotle known it have been reputed the ground of his despair with more credit then that petty Problem of the frequent and irregular Reciprocation of Euripus we have selected only six as the most considerable and such whose solution may serve as a bright tapor to illuminate the reason of the Curious who desire to look into the dark and abstruce Dihoties of the rest SECT II. The First Capital Difficulty WHether that Space in the Tube betwixt the upper extreme thereof and the Quicksilver delapsed to the altitude only of 27 digits be really an entire and absolute Vacuity Concerning this some there are who confidently affirm the space between the superfice of the Quicksilver defluxed and the superior extreme of the Tube to be an absolute COACERVATE VACUITIE such as may be conceived if we imagine some certain space in the world to be by Divine or miraculous means so exhausted of all matter or body as to prohibit any corporeal transflux through the same And the Reasons upon which they erect their opinion are these subsequent This space if possessed by any Tenent must be replenished either with common Aer or with a more pure and subtle substance called Aether which some have imagined to be the Universal Caement or common Elater by which a general Continuity is maintained through all parts of the Universe and by which any Vacuity is praevented or by some exhalation from the mass of Quicksilver included in the Tube First that it is not possessed by Aer is manifest from several strong and convincing reasons 1 Because the inferior end of the Tube D is so immersed into the subjacent mass of Quicksilver below the line EF that no particle of aer can enter thereat 2 Because if there were aer in the Tube filling the deserted space CK then would not the circumambient or extrinsecal aer when the Tube is educed out of the restagnant Quicksilver and Water rush in with that violence as to elevate the remainder of the Quicksilver in the Tube from K to D up to the top C and break it open as is observed in regard that could not happen without a penetration of bodies So that if we suppose any portion of aer to have slipped into the Tube below at the subduction of the finger that closed the orifice then would not the Mercury reascending upon the inclination of the Tube down to the horizontal line KM rise up quite to the top C but subsist at OP But the contrary is found upon the experiment 4 If any portion of Aer chance to intrude into the cavity of the Tube which may come to pass either if when the superior orifice of the Tube is inverted it be not exactly obturated by the finger of the Experimentator or if at the extraction of his finger the lower eâ—treme be not immersed deep enough in the subjacent Mercury to prevent the subingress of some aer or if the orifice of the Tube educed out of the region of the subjacent Mercury and Water be not wholly deobturated at once but so as there is only some slender inlet of Aer We say if in any of these Cases it happen that some small portion of aer be admitted into the cavity of the Tube we have the evidence of our sense and the most infallible one too that the aer so admitted doth not ascend to the top C but remaine visible in certain small Bubbles such as usually mount up to the surface of seething water immediately upon the superfice of the Mercury at the altitude of 27 digits K. As if indeed the aer were attracted and in a manner chained down by the Magnetical Effluviums of the earth together with the pendent Quicksilver which having more Ansulae or Fastnings whereon the small Hooks of the Magnetical Chains exhaling from the Globe of the Earth may be accommodately fixed is therefore attracted downward more forcibly and in that respect is reputed to have the greater proportion of Gravity Again If upon the inclination of the Tube and the succeeding repletion of the same by the regurgitating Mercury that portion of aer formerly entered be propelled up to the top of the Tube C and then the Tube again reduced to its perpendicular so as the Quicksilver again deflux to K in this case the aer doth not remain at C but sinks down as formerly to K also and there remains incumbent upon the face of the Quicksilver Which Descent of the aer cannot be more probably referred to any Cause then the Attraction of the Magnetick streams of the Earth 5 Having admitted some few Bubbles of aer to slide up by the margine of the Mercury into the desert Space KC and then reclined the Tube to the altitude of the horizontal line KM you may perceive the delapsed Quicksilver not to be repelled up again quite to the top as before the irreption of aer but to make a stand when it arrives at the confines of the included aer at OP leaving so much space as is requisite for the reception of it Nor can it do otherwise without a penetration of Dimensions by the location of two Bodies in one and the same place 6 Moreover after the acquiescence of the Quicksilver at K if you stop the inferior extreme D with your finger while it remains immersed in the restagnant Quicksilver EF so as to praeclude the irreption of any more aer and then invert the Tube again the Scene of the Desert Capacity CK will be changed to the contrary extreme stopt by your finger and yet without the least sign of aer pervading the mass of Quicksilver in a kind of small stream of Bubbles contrary to what evene's when aer is admitted into the Tube in a small quantity for in that case upon the inversion of the Tube you may plainly behold an intersection between the descending Quicksilver and the ascending aer which mounts up through it in a small stream or thread of Bubbles 7 To those who conceive that a certain portion of the Circumstant Aer being forced by the compression of the restagnant Mercury in the Vessel rising higher upon the deflux of the Mercury contained in the Tube doth penetrate the sides of the Tube and so replenish the desert Capacity therein we answer that though we deny not but aer may penetrate the pores or Incontiguities of Glass since that is demonstrable in Weather Glasses and in the experiment of Sr. Kenelm Digby of making a sensible transudation of Mercury mixt with Aqua Fortis in a Bolt-head through the sides thereof if gently confricated with a Hares-foot on the outside yet cannot it be made out that therefore the Desert Capacity in the Tube is possessed with Aer for two inoppugnable reasons 1
Emission of certain Igneous or Lucid Spirits from the Organ to the Object supposing the Eye to be a kind of Glass Lantern illustrate and illustrating the Visible by its own Light 5 PLATO though He likewise avouched the Emanation of Corporeal Effluviaes from the Object doth not yet allow them to arrive quite home at the Eye but will have them to be met half way by rayes of Light extramitted from the Eye and that these two streams of External and Internal Light encountring with some Renitency reciprocal do recoyl each from other and the stream of Internal Light resilient back into the eye doth communicate unto it that particular kind of Impression which it received from the stream of Extradvenient Light in the encounter and so the Sentient Faculty comes to perceive the adspectable Form of the object at which the Radius of Internal Light is levelled This we judge to be sense of his words in Timaeo circa finem tertiae partis Simulachrorum quae vel in speculis oboriuntur vel in perspicua laevique cernuntur superficie facilis assecutio est Nam ex utriusque ignis tam intimi quam extra positi Communione ejusque rursus consensu congruentia qui passim terso laevique corpori accommodatus est necessariâ— haec omnia oriuntur quam ignis oculorum cum eo igne qui est è conspecto effusus circa laeve nitidumque Corpus sese confundit 6 EPICURUS tacitely subverting all these foundeth the Reason of Vision not in any Action of the intermediate Aer as the Stoicks and Aristotle nor in any Radious Emanation from the Eye to or toward the Object as the Pythagoreans Empedocles and Plato but in the Derivation of a substantial Efflux from the Object to the Eye 7 And as for the opinion of the excellent Monsieur Des Cartes which with a kind of pleasant violence hath so ravisht the assent of most of the Students of Physiology in the praesent Age especially such as affect the accommodation of Mechanick Maxims to the sensible operations of Nature that their minds abhor the embraces of any other those who have not heedfully perused his Dioptricks may fully comprehend it in summary thus For Sensation in Common He defines it to be a simple Perception whereby a certain Motion derived from a body conveniently objected communicated by Impression to the small Fibres or Capillary Filaments of a Nerve and by those in regard of their Continuity transmitted to the Tribunal or Judicatory Seat of the Soul or Mind which He supposeth to be the Glandula Pinealis in the centre of the Brain and there distinctly apprehended or judged of So that the Divers Motions imprest upon the slender threads of any Nerve are sufficient to the Causation of divers perceptions or that we may not eclipse his notion by the obscurity of our Expression that the Impulse or stroke given to the Nerve doth by reason of the Continuity of its parts cause another Motion in all points answerable to the first received by the External Organ to be carried quite home to the Throne of the Mind which instantly makes a respective judgment concerning the Nature of the Object from whence that particular Motion was derived In a word that only by the Variety of Strokes given to the External Organ thence to the filaments of the Nerve annexed thereto thence to the Praesence Chamber of the Soul we are informed of the particular Qualities and Conditions of every Sensible the variety of these sensory Motions being dependent on the variety of Qualities in the Object and the variety of judgments dependent on the variety of Motions communicate And for the sense of Seeing in special He conceives it to be made not by the mediation of Images but of certain Motions whereof the Images are composed transmitted through the Eye and Optick Nerve to the Centrals of the Brain praesuming the Visible Image of an Object to be only an exact representation of the motions thereby impressed upon the External Sensorium and accordingly determining the Reason of the Minds actual Discernment of the Colour Situation Distance Magnitude and Figure of a Visible by the Instruments of Sight to be this 1 The Light desilient from the adspectable Body in a direct line called by the Masters of the Opticks the Axe of Vision percusseth the diaphanous fluid Medium the Aether or most subtile substance by Him assumed to extend in a Continuate Fluor through the Universe and so to maintain an absolute Plenitude and Continuity of Parts therein 2 The Aether thus percussed by the Illuminant serving as a Medium betwixt the Object and the Eye conveyeth the impression through the outward Membranes and Humors destined to Refraction to the Optick Nerve most delicately expansed into the Retina Tunica beyond the Chrystalline 3 The Motion thus imprest on the outward Extreme of the Optick Nerve runs along the body of it to the inward Extreme determined in the substance of the Brain 4 The Brain receiving the impression immediately gives notice thereof to its Noble Tenent the Soul which by the Quality of the stroke judgeth of the Quality of the Striker or Object In some proportion like an Exquisite Musitian who by the tone of the sound thereby created doth judge what Cord in a Virginal was strook what jack strook that string and what force the jack was moved withall whether great mean or small slow or quick equal or unequal tense or lax c. This you 'l say is a Conceit of singular Plausibility invented by a Wit transcendently acute adorned with the elegant dress of most proper and significant Termes illustrate with apposite similes and praegnant Examples and disposed into a Method most advantageous for persuasion and we should betray our selves into the Censure of being exceedingly either stupid or malicious should we not say so too but yet we dare not so sacred is the interest of Truth allow it to be more then singularly Plausible since those Arguments wherewith the sage theâ—2 â—2 chap. of His Treatise of Bodies hath long since impugned it are so exceedingly praeponderant as to over-ballance it by more then many moments of Reason nor could Des Cartes himself were He now Unglorified satisfie for his Non-Retractation of this Error after his examination of their Validity by any more hopeful Excuse then this that no other opinion could have been consistent to His Cardinal Scope of Solving all the Operations of Sense by Mechanick Principles Now of all these Opinions recited we can find after mature and aequitable examination none that seems either grounded on so much Reason or attended with so few Difficulties or so sufficient to the verisimilous Explanation of all the Problems concerning the Manner of Vision as that of Epicurus which stateth the Reason of Vision in the INCURSION of substantial Images into the Eye We say FIRST Grounded on so much Reason For insomuch as it is indisputable that in the act of
parts of both Liquors and yet most certain it is that the particles of Wine possess not the same Invisible Loculaments or Receptaries that are replete with the particles of Water but others absolutely distinct because otherwise there would be as much of Water or Wine alone in the Vial as there is of both Water and Wine which in that Continent is impossible And hereupon we Conclude that to admit every distinct species to replenish the whole medium is no less dangerous then to admit that each of two Liquors confused doth singly replenish the whole Capacity or the Continent the parity of reasons justifying the Parallelism Assumption the Fifth That the visible Image being trajected through the Pupil and having suffered its ultimate refraction in that Convex Mirror the Chrystalline Humor is received and determined in that principal seat of Vision which holds no remote analogy to a Concave Mirror the Retina Tunica or Expansion of the Optick Nerve in the bottom of the eye and therein represents the Object from whence it was deradiated in all particulars to the life i. e. with the same Colour Figure and Situation of parts which it really beareth provided the Distance be not excessive The First part of this eminent Proposition that excellent Mathematician Christopher Scheinerus hath so evicted by Physical Reasons Optical Demonstrations and singular Experiments as no truth can seem capable of greater illustration and less opposition and therefore the greatest right we can do our selves or you in this point is to remit you to the observant lecture of his whole Third Book de Fundament Opticis which we dare commend with this just Elogie that it is the most Elaborate and Satisfying investigation of the Principal Seat of Vision that ever the World was enriched with and He who shall desire a more accomplisht Discourse on that formerly abstruse Theorem must encounter the censure of being either scarce Ingenious enough to comprehend or scarce Ingenuous enough to acknowledge the convincing Energy of the Arguments and Demonstrations therein alledged for the confirmation of his Thesis Radij formalitèr visorij nativam sedem esse tunicam retinam And the other is sufficiently evincible even from hence That the Sight or if you please the Interior Faculty doth alwayes judge of tâ—e adspectable form of an Object according to the Condition of the Image emanant from it at least according as it is represented by the Image at the impression thereof on the principal visory part Which is a position of Eminent Certitude For no other Cause can be assigned why the Visive Faculty doth deprehend and pronounce an object to be of this or that particular Colour but only this that the Image imprest on the Net-work Coat doth represent it in that particular Colour and no other Why when half of the Object is eclipsed by some opace body interposed the eye can speculate nor the faculty judge of no more then the unobscured half but only this that the Image is mutilated and so consisteth of onely those radii that are emitted from the unobscured half and consequently can inferr the similitude of no more Why an Object of whatever Colour appeareth Red when speculated through Glass of that Tincture but only because the Image in its trajection through that Medium being infected with redness retains the same even to its sigillation on the Expansion of the Optick Nerve Why the sight in some cases especially in that of immoderate distance and when the object is beheld through a Reversing Glass deprehends the object under a false figure but because the Image represents it under that dissimilar figure having either its angles â—etused by reason of a too long trajection through the Medium or the situation of its parts inverted by decussation of its rayes in the Glass CONSECTARY the First Now it being no less Evident then Certain that the Image is the sole cause of the Objects apparence under such or such a determinate Colour and of this or that determinate Figure it is of pure Consequence that the Image must also be the Cause of the Objects appearance in this or that determinate Magnitude especially since Figure is essenced in the Termination of Magnitude according to Euclid lib. 1. def 14. Figura est quae sub aliquo vel aliquibus terminis comprehenditur For why doth the object appear to be of great small or mean dimensions if not because the Image arriving at the sentient is great small or mean Why doth the whole object appear greater then a part of it self unless because the whole Image is greater then a part of it self To speak more profoundly and as men not altogether ignorant of the Mysteries in Opticks demonstrable it is that the Magnitude of a thing speculated may be commensurated by the proportion of the Image deradiated from it to the distance of the Common Intersection For as the Diametre of the Image projected through a perspective or Astronomical Tube on a sheet of white paper is in proportion to the Axis of the Pyramid Eversed so is the diameter of the basis of the Object to the Axis of the Pyramid Direct And hereby also come we to apprehend the Distance of the Object from the Eye for having obtained the Latitude of the object we cannot want the knowledge of its Distance and by conversion the knowledge of its distance both assists and facilitates the comprehension of its Magnitude Which comes not much short of absolute necessity since as Des Cartes Dioptrices cap. 6. hath excellently observed in these words Quoniam autem longitudo longius decurrentiam radiorum non exquisite salis ex modo impulsus cognosci potest praecedens Distantiae scientia hic in auxilium est vocanda Sic ex Gr. sâ— distantia cognoscatur esse magna Angulus visionis sit parvus res objecta longius distans judicatur magna sin verò distantia sciatur esse parva angulus Visionis sit magnus objectum judicatur esse parvum si verò distantia objecti longius dissiti sit in cognita nihilcerti de ejus magnitudine decerni potest if the Distance of an object far removed be unknown the judgment concerning the magnitude thereof must be uncertain CONSECTARY the Second Again insomuch as the Receptary of the Visible Image is that Concave Mirrour the Retina tunica we call it a Concave Mirrour not only in respect of its Figure and Use but also in imitation of that grand Master of the Opticks Alhazen who in lib. 1. cap. 2. saith thus Et sequitur ex hoc at corpus sentiens quod est in Concavo Nervi retina nimirum sit aliquantulùm Diaphanum ut appareant in eo formae lucis coloris c. Hence is it that no Image can totally fill that Receptary unless it be derived from an object of an almost Hemispherical ambite or Compass so that the rayes tending from it to the eye may bear the form of a Cone
be the segment of a great or small Circle projects the Image of an Object on a paper set at convenient distance from the tube that holds it Confused and insincere because it refracts the rayes thereof even to Disgregation so that never uniting again they are transmitted in divided streams and cause a chaos or perpetual confusion On the Contrary a Convex Lens refracts the rayes before divided even to a Concurse and Union and so makes that Image Distinct and Ordinate which at its incidence thereon was confused and inordinate And so much the more perfect must every Convex Lens be by how much greater the Sphere is of which it is a Section For as Kircher well observes in Magia parastatica if the Lens be not only a portion of a great sphere V. Gr. such a one whose diametre contains twenty or thirty Roman Palms but hath its own diametre consisting of one or two palmes it will represent objects of very large dimensions with so admirable similitude as to inform the Visive Faculty of all its Colours Parts and other discoverables in it superfice Of which sort are those excellent Glasses made by that famous Artist Eustachio Divini at Rome by the help whereof the Painters of Italy use to draw the most exquisite Chorographical Topographical and Prosopographical Tables in the World This Difference betwixt Concave and Convex Perspicils is thus stated by Kircher Art Magnae Lucis Umbrae lib. 10. Magiae part 2. Sect. 5. Hinc patet differentia lentis Conveâ—ae Concavae quod illa confusam speciem acceptam transmissamque semper distinguit optimè ordinat â—lla verò eandem perpetuo confundit unde officium lentis Convexae est easdem confusè accept is in debita distantia secundum suam potentiam distinguere ordinare And by Scheinerus in Fundam Optic lib. 3. part 1. cap. 11. thus Licet in vitro quocunque refractio ad perpendicularem semper accidat quia tamen ipsum superficie cava terminatur radij in aerem egressi potius disperguntur quà m colliguntur cujus contrarium evenit vitro Convexo ob contrariam extremitatem Rationes sumuntur à Refractionibus in diversa tendentibus vitri Convexi Concavi ob contrarias Extremitatum configurationes Concavitas enim radios semper magis divergit sicut Convexitas amplius colligit c. Now to draw these lines home to the Centre of our problem since the Rayes of a Visible Image trajected through a Convex Perspicil are so refracted as to concurr in the Visive Axe it is a clear consequence that therefore an object appears both larger in dimensions and more distinct in parts when speculated through a Convex Glass than when lookt upon only with the Eye because more of the rayes are by reason of the Convexity of its extreme obverted to the object conducted into the Pupil of the Eye than otherwise would have been For whereas some rayes proceeding from those points of the object which make the Centre of the Base of the Visive Pyramid according to the line of Direction incurr into the Pupil others emanant from other parts circumvicine to those central ones fall into the Iris others from other parts circumvicine fall upon the eye-lids and others from others more remote or nearer to the circumference of the Base of the Pyramid strike upon the Eyebrows Nose Forehead and other parts of the face the Convexity of the Glass causeth that all those rayes which otherwise would have been terminated on the Iris eye-lids brows nose forehead c. are Refracted and by refraction deflected from the lines of Direction so that concurring in the Visive Axe they enter the Pupil of the Eye in one united stream and so render the Image imprest on the Retina Tunica more lively and distinct and encreased by so many parts as are the rayes superadded to those which proceed from the parts directly confronting the Pupil On the Contrary because an Image trajected through a Concave Perspicill hath its rayes so refracted that they become more rare and Disgregate the object must therefore seem less in dimensions and more confused in parts because many of those rayes which according to direct tendency would have insinuated into the Pupill are diverted upon the Iris Eyelids and other circumvicine parts of the face Here opportunity enjoyns us to remember the duty of our Profession nor would Charity dispense should we in this place omit to prescribe some General Directions for the Melioration of sight or natively or accidentally imperfect The most common Diminutions of Sight and those that may best expect relief from Dioptrical Aphorisms and the use of Glasses are only Two Presbytia and Myopia The First as the word imports being most familiar to old men is Visus in perspiciendis object is propinquis obscuritas in remotis verò integrum acumen an imperfection of the sight by reason whereof objects near hand appear obscure and confused but at more distance sufficiently clear and distinct The Cause hereof generally is the defect of due Convexity on the outside of the Chrystalline Humor arising either from an Error of the Conformative Faculty in the Contexture of the parts of the Eye or and that mostly from a Consumption of part of the Chrystalline Humour by that Marasmus Old Age which makes the common Base of the Image Visible to be trajected so far inwards as not to be determined precisely in the Centre of the concave of the Retina Tunica And therefore according to the law of Contrariety the Cure of this frequent symptome is chiefly if not only to be hoped from the use of Convex Spectacles which determine the point of Concurse exactly in the Centre of the Retina Tunica the rayes by reason of the double Convexity viz. of the Lens and Chrystalline Humor being sooner and more vigorously united in the due place The Other being Contrary to the first and alwayes Native commonly named Purblindness Physitians define to be Obscuritus visus in cernendis rebus distantibus in propinquis verò integrum acumen a Dimness of the sight in the discernment of Objects unless they be appropinquate to the Eye The Causes hereof generally are either the too spherical Figure of the Chrystalline Humor or in the Ductus Ciliares or small Filaments of the Aranea Tunica the proper investment of the Chrystalline a certain ineptitude to that contraction requisite to the adduction of the Chrystalline inwards towards the retina tunica which is necessary to the discernment of objects at distance either of these Causes making the common Base of the Image to be determined in the Vitrious Humor and consequently the Image to arrive at the retina tunica perturbed and confused And therefore our advice is to all Purblind Persons that they use Concave Spectacles for such prolong the point of concurse untill it be convenient i. e. to the concave of the retina tunica Assumption the Sixth and last Since all objects speculated under the same
the interior angle and is called the Trochlea or Pully These two Circumactors are sirnamed Amatorij the Lovers Muscles for these are they that roul about the eye in wanton or amorous Glances And thus much of the Conformation of the Eye Now as to the Solution of our Problem viz. How the SITUATION of an object is perceived by the sight Since it is an indisputable Canon Omnem sensum deprehendere rem ad eam regionem è qua ultimò directa metione feritur that every sense doth apprehend its proper object to be situate in that part of Space from whence by direct motion it was thereby affected we may safely inferr that the Visible Object alwayes appears situate in that part of space from whence the Image thereof in a direct line invadeth the Eye and enters the Pupil thereof Which is true and manifest not only in the intuition of an object by immediate or Direct rayes but also in the inspection of Looking-Glasses that represent the object by Reflex and a pure Consequence that a Visible Object by impression of its rayes proceeding from a certain place or region must of necessity be perceived by the sight in its genuine position or Erect Form though we have the testimony both of Reason and Autopsie that the Image of every Visible is pourtraid in the Amphiblestroides in an unnatural position or Everse Form And as for that of Autopsie or Ocular Experiment Take the Eye of an Oxe or if the Anatomick Theatre be open of a man for in that the species are represented more to the life than in the Eye of any other Animal as Des Cartes in dioptrices cap. 5. Sect. 11. and having gently stript off the three Coats in the bottome in that part directly behind the Chrystalline so that the Pellucidity thereof become visible place it in a hole of proportionate magnitude in the wall of your Closet made obscure by excluding all other light so that the Anterior part theaeof may respect the light This done admoving your Eye towards the denudated part of the Chrystalline you may behold the Species of any thing obverted to the outside of the Eye to enter through the Chrystalline to the bottom thereof and there represented in a most lively figure as if pourtrayed by the exquisite Pencil of Apelles but whoâ—ly Eversed as in this following Iconisme Finally an object appears either in Motion or Quiet according as the Image thereof represented on the Retina Tunica is moved or Quiet only because according to the Canon in the praecedent Article touching the reason of the perception of the situation of an object the Visible is alwayes judged to be in that part of Space from which in a direct line the last impression is made upon the Sensorium And this Reason is of extent sufficient to include the full Solution also of that PROBLEM by Alexander 2. de Anima 34. so insulting proposed to the Defendants of Epicurus Material Actinobolisme Visive or the Emanation of substantial Images from the Object to the Eye viz. Why doth tâ—e Image of a man move when reflected from a Mirrour according as the man moves For this Phaenomenon we are to referr to the Variation of the parts of the Mirrour from each of which it is necessary that a fresh Reflexion of the Species be made into the Eye and consequently that the Image appear moved according to the various motions of the object The necessity of this is evident from hence if you stand beholding your face in a Glass and there be divers others standing by one at your right hand another at your left a third looking over your head in the same Glass they shall all behold your image but each in a distinct part of the Glass Whence you may also understand that in the Looking-glass is not only that Image which you behold but also innumerable others and those so mutually communicant that in the same place where you behold your nose another shall see your chin a third your forehead a fourth your mouth a fifth your Eyes c. and yet doth no one see other then a simple and distinct Image Moreover you may hence inferr that in the medium is no point oâ— Space in which there is not formed a perfect Image of the â—ayeâ— concurring therein and advenient from the same object though not from the same parts or particles thereof and consequently that in the whole Medium there are no two Images perfectly alike as also that what the Vulgar Philosophers teach that the whole Image is in the whole Space or Medium and whole in every part thereof is a manifest Falsity For though it may be said justly enough that the whole Image i. e. the Aggregate of all the Images is in the whole Space yet is there no part of that Space in which the whole Image can be To this place belongs also that PROBLEM Why doth not the right hand of the Image respond to the right of the object but contrariwise the left to the right and right to the left The Cause whereof consisteth onely in the Images Confronting the Object or as Plato in Timaeo most perspicuously expresseth it quia contrarijs visus partibus ad contrarias partes â—it contactus Understand it by supposing a second person posited in the place of the Mirrour and confronting the first for his right hand must be opposed to the others left Nor is the reason of the Inversion of the parts of the Image other than this that the rayes emitted from the right side of the object are reflected on the left and â— Contra. Just as in all Impressions or Sigillations the right side of the Antitype responds to the left of the type Consule Aquilonium lib. 1. opt proposit 46. And as for the reason of the Restitution of the parts of the Image to the right position of the parts of the object by two Mirrours confrontingly positeâ— it may most easily and satisfactorily be explained by the Decussation of the reflected rayes To Conclude We need not advertise that the Optical Problems referrible to this place are if not infinite so numerous as to require a larger Volume to their orderly Proposition and Solution than what we have designed to the whole of this our Physiology Nor remember you that our principal Scope in this Chapter was only to evince the Praeâ—â—inence of Epicurus Hypothesis above all others concerning the Reason and Manner of Vision and this by accommodating it to the Verisimilous Explanation of the most Capital Difâ—â—culties occurring to a profound inquest into that abstruse subject All therefore that remains unpaid of our praesent Debt is modestly to referr it to your equitable Arbitration Whether we have deserted the Doctrine of the Aristoteleans touching this theorem and addicted ourselves to the Sect of the Epicureans on any other Interest but that sacred one of Verity which once to decline or neglect upon the sinister praetext of vindicating any Human
mighty hand or most potent Energy in the production of Colours For supposing three kinds of Salt in all natural Concretions the first a Fixt and Terrestrial the second a Sal Nitre allied to Sulphur the Third a Volatile or Armoniac referrible to Mercury and that all bodies receive degrees of Perspicuity or Opacity respondent to the degrees of Volatility or Terrestriety in the Salts that amass them they thereupon deduce their various Colours or visible Glosses from the various Commistion of Volatile or Tralucent Salts with Fixt or obscure Now notwithstanding all these Sects are as remote each from other as the Zenith from the Nadir in their opinions touching the Nature and Causes of Colours as to all other respects yet do they generally Concur in this one particular 〈◊〉 〈◊〉 〈◊〉 〈◊〉 〈◊〉 Colores esse Cohâ—rentes corporibus that Colours are CONGENITE or COHAERENT to bodies Which being manifestly repugnant to reason as may be clearly evinced as well from the Arguments alledged by Plutarch 1. advers Colot to that purpose as from the result of our whole subsequent discourse concerning this theorem we need no other justification of our Desertion of them and Adhaerence to that more verisimilous Doctrine of Democritus and Epicurus 〈◊〉 〈◊〉 〈◊〉 〈◊〉 〈◊〉 Colorem Lege esse or more plainly in the words of Epicurus 〈◊〉 〈◊〉 〈◊〉 〈◊〉 〈◊〉 Colores in corporibus gigni juxta quosdam respectu visus ordines positusque The Probability of which opiâ—â—â—n that we may with due strictness and aequâ—nâ—mity examine and 〈◊〉 whâ—t we formerly delivered in our Oâ—igine of Qualities touching thâ— possible Causes of an inassignable Variety of Colours We are briefly to advertise First That by the word 〈◊〉 〈◊〉 〈◊〉 〈◊〉 〈◊〉 Bodies we are not to understand Atoms or simple bodies for those are generally praesumed to be devoyd of all Colour but 〈◊〉 〈◊〉 〈◊〉 〈◊〉 〈◊〉 Concretions or Compounds Secondly that Epicurus in this text according to the litteral importance thereof and the Exposition of Gassendus his most judicious and copious Interpreter had this and no other meaning That in the Extrems or superficies of all Concretions there are such certain Coordinations and Dispositions of their component particles which according to our First Assumption in the immediately praecedent Chapter borrowed from the incomparable Bullialdus are never contexed without more or less of Inaequality as that upon the incidence of Light they do and must exhibit some certain Colour or other respective to their determinate Reflection and Refraction or Modification of the rayes thereof and the position of the Eye that receives them That from these superficial Extancies and and Cavities of bodies are emitted those substantial Effluviaes constituting the visible Image which striking upon the primary Organ of Vision in a certain Order and Position of particles causeth therein a sensation or Perception of that particular Colour But that these Colours are not really Cohaerent to those superficial particles so as not to be actually separated from them upon the abscedence of Light and consequently that Colours have no Existence in the Dark Moreover that the substance of Light or the minute particles of which its beams consist are necessarily to be superadded to the superficial particles of bodies as the Complement nay the Principal part of Colour as may be inferred from these words of Epicurus registred by Plutarch 1. advers Colot Quinetiam hâc parte luce viz. seclusa noâ— video qui dicere liceat corpora quae in tenebris in conspicua sunt colorem habere Of which persuasion was also that admirable Mathematician Samius Aristarchus who positively affirmed apud Stobaeum in Ecl. Phys. 19. Incidentem in subjectas res Lucem Colorem esse ideoque constituta in tenebris corpora colore prorsùs destitui To which doubtless Virgil ingeniously alluded in his Ubi Coelum condidit Umbra Iupiter rebus nox abstulit atra Colorem And Lucretius in his Qualis enim coecis poterit Color esse tenebris Lumine qui mutatur in ipso propterea quod Recta aut obliqua percussus luce refulget c. And lastly that Light doth create and vary Colours according to the various condition of the minute Faces or sides of the Particles in the superfice which receive and reflect the incident rayes thereof in various Angles toward the Eye SECT II. HAving thus recited explicated and espoused the Conceptions of Epicurus of the Creation of Colours it behoves us to advance to the Examination of its Consistency with right reason not only in its General capacity but deduction and accommodation to Particulars But First to praevent the excess of your wonder at that so Paradoxical assertion of his That there are no Colours in the dark or that all colours vanish upon the Amotion or defection of Light we are to observe that it is one thing to be Actually Colorate and another to be only Potentially or to have a Disposition to exhibit this or that particular Colour upon the access of the Producent Light For as the several Pipes in an Organ though in themselves all aequally Insonorous or destitute of sound have yet an equal Disposition in respect of their Figuration to yield a sound upon the inflation of Wind from the Bellows and as the seeds of Tulips in Winter are all equally Exflorous or destitute of Flowers but yet contain in their seminal Virtues a Capacity or Disposition to emit various coloured flowers upon the access of fructifying heat and moysture in the Spring so likewise may all Bodies though we allow them to be actually Excolor in the Dark yet retain a Capacity whereby each one upon the access and sollicitation of Light may appear clad in this or that particular Colour respective to the determinate Ordination and Position of its superficial particles To inculcate this yet farther we desire you to take a yard of Scarlet Cloth and having extended it in an uniform light observe most exactly the Colour which in all parts it bears Then extend one half thereof in a primary light i. e. the immediately incident or direct rayes of the Sun and the other in a secondary or once reflected light and then though perhaps through the praeoccupation of your judgment you may apprehend it to be all of one colour yet if you engage a skilful Painter to pourtray it to the life as it is then posited He must represent the Directly illuminate half with one Colour viz. a bright and lightsome Red and the Reflexly illuminate half with another i. e. with a Duskish or more obscure Red or shamefully betray his ignorance of Albert Durers excellent Rules of shadowing and fall much short of your Expectation This done gently move the extended Cloth through various degrees of Light and shadow and you shall confess the Colour thereof to be varied upon each remove respondent to the degree of Light striking thereupon Afterward fold the Cloth as Boyes do paper for Lanterns or lay it
in waves or pleights of different magnitude and you shall admire the variety of Colours apparent thereon the lâ—minent and directly illustrate parts projecting a lively Câ—â—nation the Lateral and averted yeilding an obscure sanguine clouded with Murrey and the Profound or unillustrate putting on so perfect sables as no colour drawn on a picture can counterfeit it to the life but the deadest Black Your Sense thus satisfied be pleased to exercise your Reason a while with the same Example and demand of your self Whether any one of all those different Colours can be really inhaerent in the Cloth If you pitch upon the Scarlet as the most likely and proper then must you either confess that Colour not to be really inhaerent since it may in less than a moment be varied into sables only by an interception of Light or admit that all the other Colours exhibited are aequally inhaerent which is more we praesume then you will easily allow And therefore you may attain more of satisfaction by concluding that indeed no one of all those Colours is really so inhaerent in the cloth as to remain the same in the absence of Light but that the superficial particles of the Cloth have inhaerent in them ratione Figurae Coordinationis Positus such a Disposition as that in one degree of Light it must present to the eye such a particular colour in another degree a second gradually different from that in another a third discriminate from both until it arrive at perfect obscurity or Black And if your Assent hereto be obstructed by this DOUBT Why that Cloth doth most constantly appear Red rather then Green Blew Willow c. you may easily expede it by admitting that the Reason consisteth only herein that the Cloth is tincted in a certain Liquor whose minute Particles are by reason of their Figure Ordination and Disposition comparate or adapted to Refract and Reflect the incident rayes of Light in such a manner temperation or modification as must present to the eye the species of such a Colour viz. Scarlet rather then a Green Blew Willow or any other For every man well knows that in the Liquor or Tincture wherein the Cloth was dyed there were several ingredients dissolved into minute pâ—rticles and that there is no one Hair or rather no sensible part in the superfice thereof whereunto Myriads of those dissolved particles do not constantly adhere being agglutinated by those Fixative Salts such as Sal Gemmae Alum calcined Talk Alablaster Sal Armoniack c. wherewith Dyers use to graduate and engrain their Tinctures And therefore of pure necessity it must be that according to the determinate Figures and Contexture of those adhaerent Granules to the villous particles in the superfice of the Cloth such a determinate Refraction and Reflection of the rayes of Light should be caused and consequently such a determinate species of Colour and no other result therefrom Now insomuch as it is demonstrated by Sense that one and the same superfice doth shift it self into various Colours according to its position in various degrees of Light and Shadow and the various Angles in which it reflecteth the incident rayes of Light respective to the Eye of the Spectator and justly inferrible from thence by Reason that no one of those Colours can be said to be more really inhaerent than other therein all being equally produced by Light and Shadow gradually intermixt and each one by a determinate Modification thereof What can remain to interdict our total Explosion of that Distinction of Colours into Real or Inhaerent and False or only â—pparent so much celebrated by the Schools For since it is the Genuine and Inseparable Propriety of Colours in General to be Apparent â—o suppose that any Colour Apparent can be False or less Real than other is an open Contradiction not to be dissembled by the most specious Sophistry as Des Cartes hath well observed in Meteor cap. 8. art 8. Besides as for those Evanid Colours which they call 〈◊〉 〈◊〉 〈◊〉 〈◊〉 〈◊〉 meerly Apparent ones such as those in the Rainbow Parheliaes Paraselens the trains of Peacocks necks of Doves Mallards c. we are not to account them Evanid because they are not True but because the Disposition of those superficial particles in the Clouds and Feathers that is necessary to the Causation of them is not Constant but most easily mutable in respect whereof those Colours are no more permanent in them than those in the Scarlet cloth upon the various position extension plication thereof And Charity would not dispense should we suppose any man so obnoxious to absurdity as to admit that the greater or less Duration of a thing doth alter the Nature of it Grant we for Example that the particles of Water constituting the rorid Cloud wherein the Rainbow shews it self were so constant in that determinate position and mutuall coordination as constantly to refract and reflect the incident beams of the Sun in one and the same manner and then we must also grant that they would as constantly exhibite the same Species of Colours as a Râ—inbow painted on a table but because they are not and so cannot constantly refract and reflect the irradiating light in one and the same manner it is repugnant to reason thereupon to conclude that the Instability of the Colours doth detract from the Verity or Reality of their Nature For it is only Accidental or Unessential to them either to be varied or totally disappear So that if you admit that Sea Green observed in the Rainbow to be less True than the Green of an Herb because its Duration is scarce momentany in comparison of that in the Herb you must also admit that Green in the Herb which in a short progress of time degenerates into an obscure yellow to be less true than that of an Emrauld because its Duration is scarce momentany in comparison of thâ—â— of the Emrauld But perhaps Praejudice makes you yet inflexible and therefore you 'l farther urge thâ—t the Difficulty doth cheifly concern those Evanid Colours which â—â—e appinged on Bodies reflecting light by Prisms or Triangular Glasseâ— vulgarly called Fools Paradises because these seem to have the least of Reality among all other reputed meerly Apparent And in case yâ—â— assault us with this your last Reserve we shall not desert our station for want of strength to maintain it For that those Colours are as Real as any other the most Durable is evident even from hence that they have the very same Materials with all other i. e. they are the substance of Light it self reflected from those objected Bodies â—nd what happens not to those eyes that speculate them without a Prism twice refracted Experience dâ—monstrates that if a man look intently upon a polite Globe in â—hat part of it superfice from which the incident Light is reflecteâ— in direct lines toward his eye He shall perceive it to appear clad in another Colour than when He looks upon it from
any other part of the Medium toward which the Light is not reflected and 〈…〉 He have no reason why He should not account both those Difâ—â—â—ent Colours to be True the Reflection of light which varieth the Apparition according to the various Position of the eye in several parts of the Medium nothing diminishing their Verity If so why should not those Colours created by the Prism be also reputed Real the Refraction of Light which exhibiteth other Colours in the objected Bodies than appear in them without that Refraction nothing diminishing their Reality By way of COROLLARY let us here observe that the Colours created by Light reflected from objects on the Prism and therein twice refracted are Geminated on both sides thereof For insomuch as those Colours are not appinged but on the Extremes of the Object or where the supâ—rfice is unequal for if that be Plane and Smooth it admits only an Uniform Colour and the same that appears thereon when beheld without the Prism therefore are two Colours alwayes observed in that Extreme of the Object which respecteth the Base of the Triangle in the Glass and those are a Vermillion and a Yellow and two other Colours in that extreme which respecteth the Top of the Triangle and those are a Violet blew and a Grass green And hence comes it that if the Latitude of the Superfice be so small as that the extremes approach each other sufficiently near then are the two innermost Colours the Yellow and Green connected in the middle of the Superfice and all the four Colours constantly observe this order beginning from the Base of the Triangle a Vermillion Yellow Green and Violet beside the inassignable variety of other Intermediate Colours about the Borders and Commissures We say Beginning from the Base of the Triangle because which way soever you convert the Prism whether upward or downward to the right or to the left yet still shall the four Colours distinguishably succeed each other in the same method from the Base however all the rayes of Light reflected from the object on the Prism and trajected through it are carried on in lines parallel to the Base after their incidence on one side thereof with the obliquity or inclination of near upon thirty degrees and Refraction therein to an Angle of the same dimensions that issuing forth on the other side they are again Refracted in an Angle of near upon 30 degrees and with the like obliquity or inclination These Reasons equitably valued it is purely Consequent that no other Difference ought to be allowed between these Emphatick or as the Peripatetick False Colours and the Durable or True ones than only this that the Apparent deduce their Creation for the most part from Light Refracted in Diaphanous Bodies respectively Figurated and Disposed and sometimes from light only reflected but the Inhaerent or True as they call them deduce theirs from Light variously Reflexed in opace bodies whose superficial particles or Extancies and Cavities are of this or that Figure Ordination and Disposition Not that we admit the Durable Colours no more than the Evanid to be Formally as the Schools affirm Inhaerent in Opace bodies whose superficial Particles are determinately configurate and disposed to the production of this or that particular species of colouâ—â— and no other but only Materially or Effectively For the several species of Colours depend on the several Manners in which the minute particles of Light strike upon and affect the Retina Tunica and therefore are we to conceive that opâ—â—e Bodies reflecting Light do create Colours only by a certain Modification or Temperation of the reflected light and respondent Impression thereof on the Sensory no otherwise than as a Needle which though it contain not in it self the Formal Reason of Pain doth yet Materially or Effectively produce it when thrust into the skin of an Animal for by reason oâ— its Motion Hardness and Acuteness it causeth a dolorous sensation in the part perforated To diminish tâ—â— Difficulty yet more we are to recognize thâ—t the First Matter or Catholique Principles of all Material Natures are absolutely devoyd of all Sensible Qualities and that the Qualities of Concretions such as Colour Sound Odour Sapor Heat Cold Humidity Siccity Asperity Smoothness Haâ—dness Softness c. are really nothing else but various MODIFICATIONS of the insensible particles of the First Matter relative to the vaâ—ious Organs of the Senses For since the Orgâ—ns of the Sight Hearing â—asting Smelling and Touching have each a peculiar Contexture of the insensible particles that compose them requisite it is that in Concretions there should be various sorts of Atoms some of such a special Magniâ—â—â—â— Figure and Motion as that falling into the Eye they may conveniently move or affect the Principal Sensory and therein produce a sensation of themselves and that either Grateful or Ingratefull according as they are Commodious or Incommodious to the small Receptaries thereof for the Gratefulness or Ingratefulness of Colours ariseth from the Congruity or Incongruity of the particles of the Visible Species to the Receptaries or smâ—ll Pores in the Retina Tunica Some in like mâ—nner that may be convâ—nient to the Organ of Hearing Others to that of smelling c. So that though Atoms of all sorts of Magnitude Figure and Motion contexed into most minute Masses arrive at all the Organs of Sense yet may the Eye only be sensible of Colour the Ear of Sound the Nostrils of Odour c. Again that Colour Sound Odour and all other sensible Qualities are 〈◊〉 according to the various situation order addition detraction transposition of Atoms in the same manner as Words whereof an almost infinite â—ariety may be composed of no more then 24 Letters by their various sitâ—â—tion order addition detraction transposition as we have more copâ—â—â—sly discoursed in our precedent Original of Qualities SECT III. TO descend to Particulars It being more than probable that the various species of Colours have their Origine from only the various Manners in which the incident particles of Light reflected from the exteriours of Objects strike and affect the principal sensory it cannot be improbable that the sense of a White Colour is caused in the Optick Nerve when such Atoms of light or rayes consisting of them strike upon the Retina Tunica as come Directly from the Lucid Fountain the Sun or pure Flame or Reflexedly from a body whose superficial particles are Polite and Sphaerical such as we have formerly conjectured in the smallest and hardly distinguishable Bubbles of Froth and the minute particles of Snow And as for the perception of its Contrary Black generally though scarce warrantably reputed a Colour we have very ground for our conjecture that it ariseth rather from a meer Privation of Light than any Material Impression on the sensory For Blackness seems identical or coessential with Shadow and all of it that is positively perceptible consisteth in its participation of Light which alone
causeth it not to be absolutely Invisible And hence is it that we have several Degrees or gradual Differences of Black comparative to the several degrees of shadow progressing till we arrive at perfect Darkness and that we can behold nothing so black which may not admit of deeper and deeper blackness according to its greater and greater recess from light and nearer and nearer access to absolute Opacity To reason therefore is it consonant that all Bodies whose natural Hew is Black are composed of such insensible particles whose surfaces are scabrous rough or craggy and their Contexture so Rare or loose as that they rather imbibe or swallow up the incident rayes of light than reflect them outwardly toward the eye of the Spectator Of this sort the most memorable yet discovered is the Obsidian stone so much admired and celebrated among the Romans whose substance being conflated of scabrous and loosely contexed Atoms causeth it to appear a perfect Negro though held in the Meridian Sun-shine because the rayes invading it are for the most part as it were absorpt and stifled in the small and numerous Caverns and Meanders variously interspersed among its component particles Which common and illiterate eyes beholding delude their curiosity with this refuge that it hath an Antipathy to Light and doth therefore reflect it converted into shadows The Generation of the Two Extreme and Ground Colours White and Black being attained by this kind of inquest into the Rolls of reason the Former deriving it self from Light either immediately and in direct lines profluent from its fountain or by reflection from bodies whose superficial particles are sphaerical and polite the Later from the Negation of Light there can be no great difficulty remaining concerning the Genealogy of all other INTERMEDIATE ones since they are but the off-spring of the Extreme arising from the intermission of Light and shadow in various proportions or more plainly that the sense of them is caused in the Retina Tunica according to the variety of Reflections and Refractions that the incident Light suffers from the superficial particles of objects in manner exactly analogous to that of the Evanid Colours observed in sphaerical Glasses replete with Water in Prismes interposed betwixt the object and eye in angular Diamonds Opalls c. For even our sense demonstrates that they are nothing but certain Perturbations or Modifications of Light interspersed with Umbrellaes or small shadows The Verisimility of this may be evinced from the Sympathy and Antipathy of these intermediate Colours among themselves For the Reason why Yellow holds a sympathy or symbolical relation with Vermillion and Green and Green with Sky-colour and Yellow as the experience of Painters testifieth who educe a yellow Pigment out of Vermillion and Green in due proportions commixt upon their Palatts and reciprocally Green out of Yellow and Sky-colour in unaequal but determinate quantities contempered is no other but the Affinity of their respective Causes or only gradually different manners of Light reflected and refracted and intermixt with minute and singly imperceptible shadows And on the contrary the Reason of the Antipathy or Asymbolical relation betwixt a saffron Yellow and a Caerule betwixt a Green and a Rose colour into which a saffron yellow degenerates and betwixt a Yellow and Purple into which a Caerule degenerates can be nothing else but the Dissimilitude or Remoteness of their respective Causes since things so remotely Discrepant are incapable of Conciliation into a Third or Neutral or rather Amphidectical Nature but by the mediation of something that is participant of both This the Philosopher glanced at in his Colores misceri videntur quemadmâ—dum soni ita enim qui eximium quoddam proportionis genus servant hi Consonantiarum more omnium suavissimi sunt ceu purpâ—reus puniceus c. de sens sensil cap. 3. We say that all these Intermediate Colours emerge from the various intermistion of Light and small shadows because to the production of each of them from reflected or refracted Light or both the interposition of minute and separately invisible shadows is indispensably Necessary Which may be evidenced even from hence that Colors are not by Prismes appinged on bodies but in their Margines or Extremes there where is not only the general Commissure of Light and Shadows but also an Inaequality of superfice which by how much the more scabrous or rough by so much the more are the Colours apparent thereon ampliated in Latitude For since there is no superfice however smooth and equal to the sense devoid of many Extancies and Cavities as we have more then once profestly declared it is of necessity that betwixt the confronting sides of the Extancies reflecting the rays of light hither and thither there should be intercedent small shadows in the interjacent Cavities from which no light is reflected And hence is it that in an object speculated through a Prism the Caerule colour appears so much the more Dense and lively by how much the nearer to the limbus or Extreme of the Object it is appinged because in that place is the greater proportion of small shadows and è contra so much more Dilute and Pale by how much farther it recedeth from the Margin insomuch that it degenerates or dwindles at last into weak Sea-Green or Willow in its inmost part because in that place is the greater proportion of Light Conformable to that rule of Athanas. Kircher Art Magn. Lucis Umbrae lib. 1. part 2. cap. 1. Differunt autem Umbra Fulgores majore minore vel candore nigrore prout vel Fonti lucis aut tenebrarum propriores fuerint vel à fonte longius recesserint in quo luce obscuritate summa sunt utraque Unde patet quantò Fulgores a luce magis recesserint tanto plus Nigredinis quantò a tenebris magis recesserint Umbrae diminuto nigrore tanto plus albedinis acquirere quae omnia Visus judicare potest The same proportionately we conceive to hold good also in all Bodies whose Colours are Genuine or apparent to the naked Eye chiefly because we may lawfully conceive that every particle of every hair in a Scarlet or Violet coloured Cloth is consimilar in disposition to the particles in the extremes of an Object speculated through a Prism and hold it purely Consequential thereupon that light may arrive at the Eye from them with the like Reflections and Intermistion with shadows as from the extremes of the Reflectent Body through the Glass which advanceth its commixture with small shadows And what we affirm of Scarlet and Violet may also with no less Congruity be accommodated to Yellow and Sea-Green allowing the same proportion and modification of Light and Shadows in them as in that part of the superfice of any other body on which the Prism doth appinge them and in like manner to all other Colorate objects whose Tinctures bear any Affinity to either of these four specified or arise from
Appulse or Motion of the Aether or most subtile and so most agile matter in the Universe which is meerly praecarious and never to be conceded by any who fears to ensnare himself in many inextricable Difficulties Incongruities and Contradictions in the deducement of it through all the Phaenomena of Light Colours and Vision all that we can allow him as to this particular besides our thanks for his laborious Endeavours is that close of Phaetons Epitaph Magnis tamen excidit ausis CHAP. V. THE NATURE OF LIGHT SECT I. IN our three immediately praecedent Chapters we have often mentioned the RAYES OF LIGHT as the Material Principle both of all Visible Species and Colours and that we may not leave our Reader unsatisfied in any particular the communication whereof seems necessary or advantageous to His full comprehension of all our Conceptions relating to those Arguments or any other of Affinity to them that may hereafter occurr we judge it our Duty here to let him clearly know What Notion we have of the Nature of that so admirably glorious and universally comfortable an Entitie Light By the Rayes of Light we understand certain most tenuious streams of Igneous Particles in a continued fluor and with ineffable pernicity succeding each other in direct lines either immediately from their Lucid Fountain or mediately from solid bodies reflecting them towards the eye and sensibly affecting the same This Description may receive somewhat more both of perspicuity and credit if we consider the parallelism or analogy that each distinct Ray of Light holds to a stream of water exsilient from the Cock of a Cistern or tube of an Artiâ—icial Fountain For the reason why a stream of water issues from a tube in a kind of arch and flows to some distance from its source through the aer is only this that the particles of Water first exsilient upon the remove of the stopple or obstacle are so closely and contiguously pursued by other particles immediately following and those again by others indesinently emanant that they are impelled forward and driven on with such rapidity as overcomes their natural propensity to direct descent by reason of their Gravity and carries them in a tense line from the vent so long as their impulse is superior to that of their Gravity which encreasing more and more in each degree of distance doth at length become victor over the force of the Motion and praecipitate them downright And as this gradual Tensity or Rigidity of a stream of Water ariseth to it only from the Pressure or impulse of the Antecedent particles by the Consequent in an uninterrupted succession so may we conceeve that a Ray of Light or Wand many of our Modern and most discovering Philosophers call a stream of Light Virgula Lucis and that by an unstrained Metaphor consisting of many rayes seemingly united such as we observe shining in a room through some hole in the Window or other inlet doth therefore become in a manner Tense or Direct only because the particles first emanant from the Lucid Fountain are so urged and prest on by the subsequent and those again by others with equal pernicity that they cannot deflect from a direct line or obey the inclination of their Gravity until some solid Body interposed cut off the fluor by interrupting the succession and then the Tensity or Pressure ceasing the Particles become incontiguous and disappear as is observable upon closing the inlet through which a stream of Light is admitted into an otherwise â—pace room For immediately the successive supply of luminous particles being intercepted the Antecedent droop fail and surrender that part of space which they possest with splendour sufficient to affect the sense to the horrid encroachment of Darkness This full Comparison praemised we shall comply with opportunity and here concisely observe 1 That Aquilonius and most other Opticomathematicians do excellently distinguish Light into so many gradual Differences as are the Reflections of which it is capable denominating that Light Primary whereby a Body is immediately or in direct lines from the Lucid Fountain illustrated that Secondary which reflected from one solid body illuminates aâ—other that a Third Light which illuminateth a body after two Reflections from others and so forward up to the Centenary and Millenary light if at least it be capable of so many reflections from bodies most solid and polite 2 That Light at Second hand is more weak than at First at Third than at Second at Fourth than at Third c. or that Light becomes so much Weaker by how many more Reflections it hath suffered Not as is vulgarly concluded that a Reflex ray is less Tense or the successive pressure of its particles less violent or rapid than those of a Direct for the motion of Light however frequently reflected is incomprehensibly swift but that every reflection doth much diminish it some rayes being always diverted and scattered into other parts of the medium by reason of the Asperity or Inaequality of the particles in every superfice and so there being no superfice that remits in a direct line the full number of rayes some have adventured to say scarce half so many as it received and consequently the eye receiving fewer and fewer rayes successively from every Reflectent must be more weakly affected and moved by the thin remainder For if all the rayes of the Sun directly incident on a Wall were thence reflected on another wall situate at a right angle the Second wall would be fully as luminous as the First and consequently the Secondary light would be as strong and resplendent as the Primary but since the superfice of the First Wall is unequal and scabrous it must of necessity come to pass that though many of the rayes incident thereon are from thence projected on the Second yet as many are repercussed into other regions of the Medium some upward others downward some to the right hand others to the left c. according to the various faces or sides of the small particles with asperity contexed in the superfice of each stone therein So that one half if not the major part of the directly incident rayes being diverted from the Second Wall the Light thereon appearing must be proportionately less strong and fulgent than that which illuminates the First By the same reason if the Second Wall by reverberation derive the Light to a Third it must likewise play the Publican and remit but half so many rayes as it received from the First and so must the Third transmit a thinner stock of light to a Fourth and a Fourth to a Fifth c. If this Example seem scarce praegnant enough let us descend into a deep Pit or with the Troglodites creep into the bowels of some subterraneous Cavern and there our sense will demonstrate that multiplied Reflections of Light gradually diminish it even to absolute insensibility For the rayes of the Sun falling into the aperture of
stiffly cohaerent particles and 〈◊〉 from a most solid into an oyly substance not so much by 〈…〉 â—ymbolisme or Affinity of nature that Salt Nitre and Sulphur whicâ—â—eing added to Sand Flints and many Metals promote the solution 〈…〉 fire have yet no accelerating but a retarding energy upoâ— Turpentine Balsome Myrrh c. in the extraction of their Oyls or 〈◊〉 that all Waters or Spirits extracted from Saâ—ine and Metalline nature are most convenient Menstruaes for the solution of Metals Minerals not 〈◊〉 much in respect of their Corrosion as similitude of pores and particles and consequently that every Concretion requires to its dissolution some 〈◊〉 dissolvent that holds some respondency or analogy to its contexture 〈◊〉 yet have we no reason therefore to abandon our Assumption that 〈◊〉 dissolution of one body by the subingression or insinuation 〈…〉 another must arise from the greater subtility of particles 〈…〉 until it be commonstrated to us that a Body whose 〈…〉 can penetrate another Body whose Pores are more 〈…〉 whereto is demonstrated to us by the frequent Experimentâ— of 〈◊〉 And therefore the Reason Why Oyle Olive doth pervade some Bodies which yet are impenetrable even by spirit of Wine by â—aimundus Lullius and after him by Libavius and Quercetan accounted the true Sulphur and Mercury of Hermetical Philosophers extracted from a Vegetable for the solution of Gold into a Potable substance and the Confection of the Great Elixir and as General a Dissolvent as that admired but hardly understood Liquor Alkahest of Paracelsus if not the same can be no other but this that in the substance of Oyle are some Particles much more subtile and penetrative than any contained in the substance of Wine though those subtile particles are thinly interspersed among a far greater number of Hamous or Hooked particles which retard their penetration Thus also in that affrighting and Atheist-converting Meteor Lightning seem to be contained many particles much more exile and searching than those of our Culinary Fires because it sometimes dissolves the hardest of Metals in a moment which preserveâ— its integrity for some hours in our fiercest reverberatory furnaces Which Lucretius well expresseth in this Tetrastich Dicere enim possis caelestem Fulminis ignem Subtilem magis e parvis constare Figuris Atque ideo transire foramina quae nequit ignis Noster hic elignis ortus taedaque creatus Secondly the Qualities Consequent to Figure are SMOOTHNESSE and its contrary ASPERITY Not that if we appeal to the judgement of the sense the superfice of a Body may not be smooth though it consist of angulouâ— Atoms or rough though composed of plain and polite Atoms for all Atoms as well as their Figures are so Exile as that many of them that are angular may cohaere into a mass without any inequality in the superfice deprehensible by the sense and on the contrary many of those that are plane and polite may be convened and concreted into such masses as to make angles edges and other inequalities sufficiently sensible But that if we refer the matter partly to the judicature of Reason partly to the evidence of our senses in General we cannot but determine it to arise from the Figuration of Atoms alone First to the judicature of Reason for as the mind admits nothing to be perfectly continued besides an Atom so can it admit nothing to be exquisitely smooth besides either the whole superfice of an Atom â—f the same be orbicular oval or of the like Figure or som parts of it if the same be tetrahedical hexahedrical or of some such poligone figure Because look by what reason the mind doth conclude the superfice of no Concretion in nature to be perfectly continued by the same reason doth 〈◊〉 â—â—nclude the superfice of every thing seemingly most equal and polite to be â—â—râ—â—usly interrupted with asperities or eminent and deprest particles and 〈…〉 refers immediately and soleâ—y to many small masses of Atoms in 〈◊〉 Contexture coadunated like as it referrs the interruptions in the superfice of a piece of Lawne or Cambrique which to the eye and touch appears most smooth and united to the small masses of Filaments interwoven in the webb And here the Experiment of a Microscope is opportune for when a man looks through it upon a â—heet of the finest and â—mooâ—hest Venice Paper which seems to the naked eye and most exquisite touch to be equal and â—erse in all parts of it superfice He shall discern it to be so full of Eminences and Cavities or small Hills and Valleys as the most praegnant and praepared Imagination cannot suppose any thing more unequal and impolite Seâ—ondly to the Evidence of our senses in General because the very Afâ—â—ction of Pleasure or Pain arising to the sensory from the contact of the sâ—â—â—ible object doth sufficiently demonstrate that smoothness is a Quality 〈◊〉 either from such Atoms or such small masses of Atoms contexed as 〈◊〉 smooth and pleasant to the sense by reason of their correspondence 〈◊〉 â—he pores and particles of the Organ and contrariwise that â—sperity is a â—uality resulting either from such single Atoms or such most minute masses of Atoms concreted as dilacerate or exasperate the sense by reason of 〈◊〉 incongruity or Disproportion to the Contexture of the Organ as w◠〈◊〉 even to redundancy Exemplified in the Grateful and Ungrateful 〈◊〉 of each sense CHAP. XI OF THE Motive Vertue Habit Gravity and Levity OF CONCRETIONS SECT I. THe Third Propriety of the Universal Matter Atoms is Mobility or Gravity and from that fountain is it that all Concretions derive their Virtue Motive For though our deceptable sense inform us that the minute Particles of Bodies are fixt in the act of their Coadunation wedged up together and as it were fast bound to the peace by reciprocal concatenation and revinction yet from the Dâ—ssolution of all Compound natures in process oâ— time caused by the intestine Commotions of their Elementary Principles without the hostility of any External Contraries may our more judicious Reason well inferr that Atoms are never totally deprived of that their essential Faculty Mobility but are anceâ—santly agitated thereby even in the centrals of Concretions the most soâ—id and compact some tending one way others another in a perpetual 〈◊〉 of Eruption and when the Major part of them chance to â—ffect 〈…〉 the same way of emancipation then is their united force determimined â—o one part of the Concretion and motion likewise determined to one region respecting that Part. That same MOTIVE VIRTUE thereâ—ore wherewith every Compound Bodie is naturally endowed must owe â—ts â—rigine to the innate and co-essential Mobility oâ— its component particles being really the same thing with their Gravity or Impetus which yet receives its determinate manner and degree from their mutual Combination In respect whereof it necessarily comes to paâ—s that when Atoms mutually adhâ—ering vnto 〈…〉 other caâ—â—ot obey the â—mpuâ—â—e of 〈◊〉 â—â—ndency singly they are not
moved with that pernicity as if each were aâ—â—â—solute liberty but impeding and retarding each other in their progress arâ—â—â—rried with a flower motion But that more or less slow according to 〈◊〉 rate or proportion of common Resistence because always some of them are carryed to an opposite others transversly others obliquely to a difâ—â—rent region An◠〈◊〉 is it that because Atoms are at most freedom of range in 〈…〉 Concretions every degree of Density and Compactness causin◠〈◊〉 â—â—oportionate degree of Tardity in their spontaneous motions 〈…〉 the Motive Faculty not more generally than rightly conceived 〈…〉 chiefly in the spiritual or as vulgar Philosophy Aethereal Parts 〈◊〉 Concretions And whether the spirits of a thing are principaâ— deâ—â—â—mined to move thither do they not only themselves contend 〈…〉 and speed but also carry along with them the more 〈…〉 less movâ—able parts oâ— the Concretion as is superlatively 〈…〉 Voluntary motions oâ— Animals W◠〈◊〉 not here insist upon the Redargution of that Blasphemous and Absur◠〈◊〉 the formeâ— Epiâ—hitâ— always implies the later dream of 〈…〉 Atoms werâ— not only the First Matter but also the First and 〈…〉 of all things and consequently that all Motions and so all 〈…〉 â—niverse and Caused meerly by the inhaerent Mobility of them be 〈…〉 have expresly refuted the same in our Treatise against Atheism 〈…〉 1. artic ultim Especially since it is more opportune for us her◠〈…〉 that insomuch as the motion of all Atoms is supposed 〈…〉 Dâ—rect and most rapid therefore doth the Deviation as 〈…〉 of Concretions seem to arise from the Deflection Repercussion 〈…〉 Repression of the Atoms composing them For the 〈…〉 meeting of two Atoms may be in direct lines so that among 〈…〉 singlâ— percussion or repercussion overcomâ—ng the first begun 〈…〉 assembly oâ— Conventiâ—n will bear there may be caused some 〈…〉 â—hough more or less slow and their Occursations may be 〈…〉 Oblique angles and so by the same reason may ensue a 〈…〉 more or less slow but also more or less Oblique Moreâ—ve◠〈…〉 repeâ—cussion made to oblique angles there chance to 〈…〉 repercussion to angles equally oblique then must the 〈…〉 â—blâ—quity multangular according to the multiplicity 〈…〉 the Angles be very frequent and indistant the 〈…〉 at least to appearance to be of an uniform Curvity and 〈…〉 be termed a motion Circular Elliptical Helicoâ—â—al 〈…〉 aâ—cording to the condition of its Deflection and Crookedâ—â—â—◠〈…〉 observâ— thaâ— every Body whether Simple or 〈…〉 Concretion frâ—m which a Repercussion is made must 〈…〉 bâ— moveâ— the same way as is the repercust or not 〈…〉 because otherwise there can be no mutual 〈…〉 impingent body rebound from the repercutiâ—◠〈…〉 why â—excepting only the motion 〈…〉 of all Concretions doth ever suppose something that remains Unmoved or that in respect of its less motion is tantamount to a thing Unmoved because otherwise there could be no reciprocal Resistence and so all motion might both begin and repair it self Having thus premised these few fundamental Laws of Motion in General opportunity commands us to descend to the consideration of the FACULTY of Motion insomuch as it seems not to be any thing distinct from that Motive Force inhaerent in all Concretions which we have now both described and deduced from its immediate origine the Mobility of Atoms and that it is well known to all Book-men to appertain to the second species of Qualities according to the method of Aristotle To which we may add these lessons also that it comprehends the Third species of Qualities and obtains the First or Habit as its proper appendix Know we therefore that the Faculty or Power of Motion doth therefore seem to be one and the same thing with the coessential Mobility now described because every thing in Nature is judged to have just so much of Efficacy or Activity as it hath of Capacity to move either it self or any other thing And hence is it that in Nature there is no Faculty properly but what is Active because though the motions of things be really the same with their Actions yet must all motion have its beginning only from the Movent or Agent Nor can it avail to the contrary that all Philosophers have allowed a Passive Faculty to be inhaerent in all Concretions since in the strict dialect of truth that Passiveness is no other than a certain Impotency of Resistence or the Privation of an Active Power in defect whereof the subject is compelled to obey the Energy of another If you suppose an obscure Contradiction in this our Assertion and accordingly Object that therefore there must be a Faculty of Resistence in some proportion and that that Resistence is Passive we are provided of a satisfactory salvo which is that though the Active Virtue which is in the Resistent doth sometimes scarce discover it self yet is it manifest that there are very many things which make resistence only by motion which no man can deny to be an Active Faculty as when we rowe against wind and tide or strive with a Bowe in the drawing of it for all these evidently oppose our force by contrary moton And as for other things which seem to quiesce and yet make some resistence such we may conceive to make that resistence by a kinde of motion which Physicians denominate a Tonick motion like that of the Eye of an Animal when by the Contraction of all its muscles at once it is held in one fixt position Thus not only the whole Globe of the Earth but all its parts are held unmoved and first by mutual cohaerence and resist motions as they are parts of the whole and thus also may all Concretions be conceived to be made Immote not that the Principles of which they consist are not in perpetual inquietude and motion but because their parâ—â—cles reciprocally wedge and implicate each other and while some impede â—nd â—ppose the motions of others they all conspire to the Consistence of â—he whole However the more Learned and Judicious shall further dispute â—his paradoxical Argument yet dare we determine the Common Notiâ—n of a Faculty to be this that there is inherent in every thing a Prinâ—â—ple of Moving itself or Acting if not Primaryâ—which â—which the schools terme the Forme yet Secondary at least or profluent from the Forme being as it were the immediate Instrument thereof And here we cannot conceal our wonder that the Peripatetick hath not for so many ages together discovered himself to be intangled in a manifest Contradiction while on one part He affirms that there are certain Faculties flowing â tota substantia from the whole substance of a thing as if they were derived from the matter of Concretions and on the other concludes as indisputable that the Matter is absolutely devoid of all Activity as if it were not certain that the Faculties frequently perish when yet not the whole and intire substance of the thing perisheth but only the
power and break off the magnetique lines it could never be avelled and amoved from the Earth And hence is it that by how much the greater force is imprest upon a stone at its projection upward by so many more degrees of excess doth that imprest force transcend the force of the Retentive Magnetique lines and consequently to so much a greater Altitude is the stone mounted up in the Aer and è contra Which is also the Reason why the Imprest Force being most vigorous in the first degree of the stones ascent doth carry it the most vehemently in the beginning because it is not then Refracted but afterward the stone moves slower and slower because in every degree of ascention it looseth a degree of the Imprest Force until at length the same be so diminished as to come to an Aequipondium with the Contrary force of the magnetique Rays of the Earth detracting it Downward Lastly from hence is it that the perpendicular Delapse of most Bodies though of far different weights is observed to be Aequivelox contrary to that Axiome of Aristotle 2. de Caelo text 46 quo majus fuerit corpus eo velocius fertur and text 77. parvum terrae particulum si elevatu dimittatur ferri deorsum quo major fuerit velocius moveri upon which the Aristoteleans have grounded this erroneous Rule Velocitates gravium descendentium habere inter se eandem proportionem quà m gravitates ipsorum that the Velocities of Heavy bodies falling downward have the same proportion one to another as their Gravities have And the Reason of this Aequivelocity of Unequal weights seems to be this that of two Bullets the one of only an ounce the other of an hundred pounds weight dropt from the battlements of an high tower at the same instant though the Greater Bullet be attracted by more magnetique lines deradiate from the Earth yet hath it more particles to be attracted than the Lesser so that there being a certain Commensuration betwixt the Force Attractive and the quantity of Matter Attracted on either part the Force must be such as sufficeth to the performance of the motion of either in the same space of time and consequently both the Bullets must descend with equal Velocity and arrive at the surface of the Earth in one and the same moment All which that Lynceus Galilaeo well understood when in the Person of Salviatus desiring to calculate the time in which a Bullet might be falling from the concave of the Moon to our Earth and Sagredus had said thus to Him Sumamus igitur globum determinati with the great body or Globe thereof yet is it not Congregative of the whole Globe to any thing else as if the Globe of the Earth were to be united to the Moon or any other Orbe in the World Nor can it be affirmed that Gravity or this Virtue to motion Direct is conceded to the Terraqueous Orbe to the end it should at the Creation carry it self to that place which is Lowest in the Universe or being there posited constantly retain it self therein since in the Universe is neither Highest nor Lowest place but only Respectively to the site of an Animal and chiefly of Man whose Head is accounted the Highest and Feet the Lowest part in the same manner as there is no Right nor Left side in Nature but comparatively to the site of the parts in mans body and in reference to the Heavens For those Lateralities are not determined by any general and certain standard in Nature but variously assigned according to our Imagination The Hebrews Chaldeans and Persians confronting the Sun at his arising in the East place the Right side of the world in the South as likewise did all the Roman Southsayers when they took their Auguries The Philosopher takes that to be the East from whence the Heavens begin their Circumgyration and so assigns also the right hand to the South The Astronomer regarding chiefly the South and Meridian Sun accounts that the Dextrous part of Heaven which respecteth his right hand and that 's the West And Poets differing from all the rest turn their faces to the West and so assign the term of Right to the North for otherwise Ovid must be guilty of a gross mistake in that verse Utque duae dextrá zonae totidemque sinistrâ Hence is it that as the East cannot be the Right side of the World unless to Him who faceth the North so is the Vertical point of the world not to be accounted the Highest part of the Universe but onely as it respecteth the Head of a man standing on any part of the Earth because if the same man travail to the Antipodes that which was before the Highest will then be the Lowest part of the World This considered we must praefer that solid opinion of Plato that in the World there is an Extreme and a Middle Place but no Highest and Lowest to that meerly petitionary one of Aristotle that all Bodies tend toward the Centre of the Earth as to the Lowest place in the Universe How saith the offended Peripatetick the meerly Petitionary opinion of Aristotle Why do not all men admit that to be the Lowest part of the World which is the Middle or Centre thereof And is not that the Centre of the Earth And our Reply is that indeed we can admit Neither 1 Because should we allow the World to have a Middle or Centre yet is there no necessity that therefore we should concede the Centre to be the Lowest place in the World no more than that the Navil or Central part of a man should therefore be the Lowest part For to speak like men who have not enslaved their reason to praejudice what is opposed to the Miâ—dle is not suprem but Extreme and Highest and Lowest are opposite points in the same Extreme So likewise in the Terrestrial Globe whose middle part we account not the Lowest but the contrary point in the sphear since otherwiâ—e we must grant the Earth to have a double Infinity one in regard of its Centre the other in respect of the extreme points of it◠〈◊〉 according to which the Antipodes are Lowest to us and we 〈◊〉 to them 2 Wh◠〈◊〉 praetend to demonstrate that there is an â—xtreme in the Universe 〈…〉 â—here be â—o determine wherâ—â—nd whâ—t it is â—nd upon consequence 〈◊〉 the Universe hath anâ— Centre and wherâ— that Centre is T is moâ—â—â—han Galilaeo durst as appears bâ—â—hat his modest confession Nâ—scimus 〈…〉 ubi sit Universi centrum nâ—qâ—â— an siâ—â— quodque si maxime dâ—tur aliud 〈…〉 nisi punâ—tum imaginariâ—m adeoque nihilum omni faculâ—ate 〈…〉 〈◊〉 Cosmici dialog 1 pâ—g 22 Besides we see iâ— to be anâ—â—â—on very good groundâ— dâ—â—putâ—â—â—mongst the most Curious anâ— Learnâ—◠〈◊〉 oâ—â—he world whether the â—â—xt starâ— are mâ—ved about the Earth or thâ—â—arth by a Diurnal motion upon itâ— own aâ—is Whether the â—ixâ— stars 〈…〉 one and the same conâ—ave superfiâ—â— or rathâ—â— as
Habit to which any Act can 〈…〉 attributed but as a meer Privation for to be Dry is nothing else 〈…〉 want moisture yet because a Moistned body may contain more 〈…〉 Humidity therefore may it be said to be more or less Dry 〈◊〉 and a body that is imbued with less moisture be said to be dry 〈…〉 one imbued with more Thus Green Wood or such as hath 〈◊〉 extraneous moisture is commonly said to grow more and more 〈…〉 degrees as it is more and more Dehumectâ—ted and then at lengâ—◠〈◊〉 be perfectly dry when all the Aqueous moisture as well natura◠〈◊〉 â—mbibed is consumed though then also it contain a certain 〈◊〉 moâ—sture which Philosophers call the Humidum Primigentum 〈◊〉 this only Comparatively or in respect to its forme◠〈…〉 was imbueâ— with a greater proportion of Humidity For the 〈◊〉 of this we are to observe that there are Two sorts 〈…〉 compact bodies are usually humectated the one 〈…〉 â—he other Oleag nous and Fat The First is easily 〈…〉 by heat but not inflammable the other though it 〈…〉 and is as easily inflammable in regard of the many 〈…〉 is not easily exsoluble nor attenuable into 〈…〉 cohaerence of its particles To the First 〈…〉 that mâ—â—sture in Concretions which Chymists extracting 〈…〉 Vegetables because though it moâ—stens as Wate◠〈…〉 incapable of inflâ—mmation yet is it much more volatile 〈…〉 And to eâ—ther or both sorts though in a diverse respect belong 〈…〉 they call Aqua Vitae or the spirits of a Vegetable such 〈…〉 because though it doth moisten as Water yet is 〈…〉 evaporable by heat and as inflammable as 〈…〉 learn in the School of Sense that such bodie◠〈…〉 Aqueous and Lean moisture are easily 〈…〉 are humectate with the Unctuous 〈…〉 hardly Why because the Atoms of which the Aqueous doth consist are more laevigated or smooth in their superfice and so having no hooks or clawes whereby to cohaere among themselves or adhaere to the concretion are soon disgregated but those which compose the Oleaginous being entangled as well among themselves as with the particles of the body to which they are admixt by their Hamous angles are not to be expeded and disengaged without great and long agitation and after many unsuccessfull attempts of evolution Thus Wood is sooner reduced to Ashes than a stone because that is compacted by much of Aqueous Humidity this by much of Unctuous For the same reason is it likewise that a clodd of Earth or peice of Cloth which hath imbibed Water is far more easily resiccated than that Earth or Cloth which hath been dippt in oyle or melted fat And this gives us somewhat more than a meer Hint toward the clear Solution of Two PROBLEMS frequently occurring but rarely examined The one is Why pure or simple Water cannot wash out spots of Oyle or Fat from a Cloth or silk Garment which yet Water wherein Ashes have been boyled or soap dissolved easily doth For the Cause hereof most probably is this that though Water of it self cannot penetrate the unctuous body of oyle nor dissociate its tenaciously cohaerent particles and consequently not incorporate the oyle to it self so as to carry it off in its fluid arms when it is expressed or wrung out from the cloth yet when it is impraegnated with Salt such as is abundantly contained in Ashes and from them extracted in decoction the salt with the sharp angles and points of its insensible particles penetrating pervading cutting and dividing the oyle in minimas particulas the Water following the particles of salt at the heels incorporates the oyle into it self and so being wrung out from the cloth again brings the same wholly off together with it self Which dâ—ubtless was in some part understood by the Inventor of soap which being compounded 〈◊〉 Water Salt and Oyle most perfectly commixt is the most general Abstersive for the cleansing of Cloathes polluted with oyle grease turpentine sweat and the like unctuous natures for the particleâ— of oyle ambuscadoed in the soap encountring those oyly or pâ—nguous particleâ— which adhaere to the hairs and filaments of Cloth and stâ—â—n it become easily united to them and bring them off together with themselves when they are dissolved and set afloat in the Water by the incisive and diâ—â—â—ciating particles of the Salt which also is brought off at the same time by the Water which serveth only as a common vehicle to aâ—l the rest The other Why stains of Ink are not Delible with Water though decocted to a Lixirium or Lee with Ashes or commixt with soap but wiâ—◠〈◊〉 Acid juice such as of Limons Oranges Crabbs Vinegre c. 〈◊〉 Reason hereof seems to be only this that the Viâ—â—ioâ— or 〈◊〉 which â—trâ—kes the black in the Decoction of Galls Sumach or other 〈◊〉 Ingredients being Acid and so consisting of particles congenerâ—â—s â—n figure and other proprieties to those which constitute the 〈…〉 whenever the spot of Ink is throughly moystned with an acid 〈◊〉 the vitrioâ—â—s soon united thereto and so educed together with â—t upâ—n expression the union arising propter 〈◊〉 〈◊〉 〈◊〉 〈◊〉 〈◊〉 from the Similitude of their two natures For there always is the most easy and perfect union where is a Similitude of Essences or formal proprieties as is notably experimented in the eduction of Cold from a mans hands or other benummed parts by rubbing them with snow in the evocation of fire by fire in the extraction of some Venoms from the central to the outward parts of the body by the application of other Venoms to the skin which is the principal cause why some Poysons are the Antidotes to others the alliciency and â—â—â—â—uation of Choler by Rhubarb c. Lastly in 〈◊〉 place we might pertinently insist upon the Causes and Manner of Coâ—â—osion and Dissolution of Metals and other Compact and Firmâ— bodies 〈◊〉 Aqua Fortis Aqua Regis and other Chymical Waters the 〈◊〉 of Salt Alume Nitre Vitriol Sugar and other Salin concreted 〈◊〉 by Water the Exhalability or Evaporability of Humid and 〈◊〉 substances and other useful speculations of the like obscure naturâ— but 〈◊〉 of these deserves a more exact and prolix Disquisition than the 〈…〉 signed to our praesent province will afford and what we have already 〈◊〉 sufficiently dischargeâ—h our debt to the Title of this Chapter CHAP. XIV Softness Hardness Flexility Tractility Ductility c. SECT I. THe two First of this Rank of Secunâ—darie Qualities HARDNESS and SOFTNESS beâ—ng so neer of Extraction and Semblance that mâ—ny have confounded them with Firmness and Fluidâ—ty in a General and looser acceptâ—tion forâ— so Virgil gives the Epitheâ—e of Soft to Water Lucretius to Aer Vaporâ— Clouds c. because a Firme bodie or such whose parts are reciprocâ—lly cohaerent and superfice more 〈…〉 apparently continued as 〈◊〉 may be Soft and on the other side a Fluid body or such whose 〈…〉 not reciprocally cohaerent nor 〈◊〉 really continued as 〈…〉 be Hard
reflects the incident rayes in a more Acute angle than a Parabolical and a Parabolical than a Spherical Art 3. A CONSECTARY Why a Plane Perspicil exhibits an objâ—ct in genuine Dimenâ—ioâ—s but a Convex in Amplified and a Concave in minorated Art 1. A Recapitulation of the principal Arguments precedent and summary of the subsequent 10 The â—â—x Muscles viz. 1 The Dâ—â—ect as the Deprâ—ment 〈◊〉 Abducent 2 And Oblique as the 2 Circumactors or Lovers Muscles Art 3. Why the Situation of an object is perceived by the sight Art 5. The same illustrate by an Experiment Art 6. Why the Motiâ—n and Quiet of obâ—ects â—re dâ—scerned by the sight Art 7. Why 〈◊〉 Images imitaâ—e the motions of tâ—eâ—r Artiâ—pes oâ— Oâ—iginals Art 8. Wâ—y the rightâ—ide â—ide of a Câ—toptrical Image respects the Lâ—ft of its Exemplar And why two Catoptrick Glasses confrontingly posited cause a Râ—stitution of the parts of the Image to the natural Form Art 1. The Argument duely acknowledged to â—e superlatively Difficult iâ— not absolutely Aâ—ataleptâ—cal Art 2. The sentence of Aristâ—tle concerning the Nature of Colours and the Commentâ—â—y of Scalâ—geâ— thereupâ—n Art 3. The opinion of Plato Art 4. Of the Pythagorean and Stoiâ—k Art 5. Of the Spagyrical Philosophers Art 6. The reason of the 〈…〉 and election of Democritus and Epicurus judgâ—â—ent touching the Generaâ—iâ—n of Colâ—uâ—s Art 7. The Text of Epicurus fully and faithfully expounded Art 1. A PARADOX That there are no Colours in the Dark Art 2. A familiar Experiment attesting the Verity thereof Art 3. The Constancy of all Artificial Tinctures dependent on the constancy of Disposition in the superficial Particles of the Bodies that wear them Art 4. That sâ— generally magnifâ—ed Distinction of Colors into Inhâ—rent and meerly Apparent redargued of manifeâ—t Câ—ntradâ—ction Art 5. The Emphatâ—â—al or Evanâ—d Coloâ—rs created by 〈◊〉 nâ— less Râ—al 〈◊〉 than the â—ost 〈◊〉 Tiâ—ctures Art 6. COROLLARY The Reasons of Emphatical Colours appinged on Bodies objected by a Prism Art 7. The true Difference of Emphatical and Durable Colour◠〈◊〉 Art 8. No Colour Formally inâ—â—erent in objects but onl◠〈◊〉 or 〈◊〉 câ—â—â—rary to the constant 〈…〉 Art 9. 〈…〉 â—arther â—indiâ—ated from Difficulty by the 〈…〉 praâ—cedeâ—◠〈…〉 oâ— the Aâ—â—mists Art 1. The Nativity of White or the reason of its percepâ—ion by the sight Art 2. Black a meet Privation of Light Art 3. The Genealogâ— of all Intermediate Color Art 4. The Causes of the Sympathy Antipathy of some Colours Art 5. The intermistion of small shadows among the lines of Light absolutely necessary to the Generation of any Intermediate Colour Art 6. Two eminent PROBLEMS concerning the Generation and Transposition of the Vermillion and Caeâ—ule appinged on Bodies by Prismes Art 7. The Solution of the Former with a rational Conjecture of the Cause of the Blew apparent in the Concave of the Heavens Art 8. The Solution of the Later Art 9. The Reasons why the Author proceeds not to investigate the Causes of Compound Colours in Particular Art 10. He confesseth the Erection of this whole Discourse on simple Conjecture and enumerates the Difficulties to be subdued by him who hopes to attain an Apodictical Knowledge of the Essence Causes of Colours Art 11. Des Cartes attempt to dissolve the chief of those Difficulties unsucsessful because grounded on an unstable Hypothesis Art 1. The Clasp or Ligament of this to the praecedent Chapter Art 2. The Authors Notion of the Rays of Light Art 3. A Parallelism betwixt a stream of Watâ—r exsilient from the Cock of a Cistern and a Ray of Light emanant from its Lucid Fountain PRAECONSIDERABLES Art 4. Light distinguisht into Primary Secondary c. Art 5. All Light Debilitated by Reflection and why Art 6. An Example sensibly demonstrating the same Art 7. That light is in perpetual Motion according to Arist. Art 8. Light why Corroborated in some cases and Debilitated in others by Refraction COROLLARY Why the Figure of the Sun both rising setting apâ—ears rather Elliptical than Sphaerical Art 9. PARADOX That the proportion of Solary Rayes reflected by the superiour Aer or Aether toward the Earth is so smaâ—l as not to be sensible Art 10. That every Lucid Body as Lucid doth emit its Rayes Sphâ—erically but as Visible Pyramidally Art 11. That Light is invisible in the pure medium Art 1. The Necessity of the Authors confirmation of the Fâ—â—st Praeconsiderable Art 2. The CORPORIETY of Light demonstrated by its jâ—st Attributes viz. 1 Locomotion 2 Resilition 3 Refraction 4 Coition 5 Disgrâ—gation 6 Igniety Art 3. Aristotles Definition of Lighâ— a meer Ambage and incomprehensible Art 4. The 〈◊〉 of Light impâ—rts not the Coexistence of two Bâ—dies in one Place contrary to the Peripatetick Art 5. Nor the motion of a Bâ—dy to be Instantaneâ—us Art 6. The Invisibilitâ— of â—ight in the limpid medium no Argument of its Immateriality as the Peripatetick praesumes Art 7. Tâ—e Corporiety of Light fully consistent with the Duration of the Sun contrary to the Peripatetick Art 8. The inâ—â—nsibility of Heat in many Lucent Bâ—dieâ— no valid Argument against the praesent Thesis that Light is Flame Attenuated Art 1. An Elogy of the sense of Hearing and the Relation of this and the praecedent Chapter Art 2. The great Affinity betwixt Viâ—ibleâ—nd â—nd Audible species in their representation of the superficial Conditions of Objects Art 3. In the Causes and manner of their Destruction Art 4. In their Actinâ—bolism or Diffusion both Sphaerical and Pyramidal Art 5. In their certifying the sense of the Magnitude Figure and otherâ— Qualities of their Originals Art 6. In the obscuration of Less by Greater Art 7. In their offâ—nce of the organs when excessive Art 8. In thâ—ir production of Heat by Multiplication Art 9. In their Variability according to the various disposition of the Medium Art 10. In their chief Attributes of Lâ—comotion Exsilitiâ—â— â—mpaction Resilition Dâ—â—gregation Congâ—egation Art 1. The Product of the Praemises concerning the points of Consent Dissent of Audible and Visible Species viz. That Sounds are Corporeal Art 2. An obstruction oâ— praejudice from the generally supposed repugnant Authâ—rities of some of the Ancients expeded Art 3. An Argument of the Corporiety of Sounds Art 4. A Second Argumenâ— Câ—ROLLARâ— Art 5. The 〈…〉 where 〈…〉 dâ—sâ—ant fâ—â—m â—he Sonant aâ—d Repâ—â—cuâ—iâ—â—â— COROLLARY 2. Art 6. Why Concaves yeild the strongest and longest Sounds COROLLARY 3. Art 7. The reason of Conâ—urrent Echoes where the Audient is near the Reflectent and remote from the sonant COROLLARY 4. Art 8. Why Echoes Monâ—phâ—n rehearâ—e so much the fewer syllables by how much nearer the audient is to the Reflectenâ— COROLLARY 5. Art 9. The reaâ—on of Pâ—lyphâ—n Echoes Art 10. A Third Argument of the Materiality of Sâ—unds Art 11. The necessity of a certain Configuration in a Sound inferred from the Distinction of one sound from another by the Sense Art 12. The same confirmed by the Aâ—ctority
Iâ—testine Cauâ—es of Corruptâ—â—n chiefly Twâ— 1 the interception of â—â—anity among the 〈◊〉 particâ—es of Bâ—dies 2 â—â—e â—ential Gravity and inâ—eparable Mobility of Atoms Art 6. The Generall Manners oâ— Ways of Generation and Corruption Art 7. Inadverâ—â—â—cy of Aristotle in making Five General 〈◊〉 of Generatiâ—â— Art 8. The special Manners of Generation innumerable and why Art 9. All sâ—â—ts oâ— Atoms not indiâ—feâ—ently coâ—petenâ— to the Constitution of all sorts of thing Art 1. Why thâ— Nature of â—otion which dâ—sâ—rved to have been the subject of the first speculatiâ—â— was resâ—rved to bâ— the Argumâ—nt of tâ—e Last in this Phâ—siology Art 2 An Epicurean Principle of â—unâ—amental concern to moâ—ion Art 3. 〈…〉 Art 〈…〉 Art 6. Emperiâ—â—â— his â—â—â—ections against that Dâ—finition of Epicâ—rus and 〈…〉 of each Art 7. That tâ—ere is motion contrary â—o thâ— Sopâ—â—sms of Parmenides Melâ—ssus Zeno Dâ—â—doâ—us and the Sceâ—ticks Art 1. 〈…〉 Art 2 The 〈◊〉 deduced from the 〈◊〉 Epicurean Pâ—â—â—cipâ—e of moâ—â—on 〈◊〉 and 〈◊〉 considâ—raâ—le Conclusions extracted from theâ—ce Art 4. 〈◊〉 or Aequanility â—he 〈◊〉 â—haracter of a Natural motionâ— and 〈◊〉 want of uniâ—ormity of a 〈◊〉 Art 5. â—he Dâ—wnwâ—rd motion 〈◊〉 Inanimates derived from â—n External Principle contrary to Aristotle Art Art 12. That the Proportion or Ration of Celerity to Celerity encreasing in the descent of Heavy things is not the same as the Proportion or Ration of Space to Space which they pervade contrary to Michael Varâ— the Mathematician Art 14 〈…〉 Art 16. The Physical Reason of that Proportion Art 17. The Reason of the Eâ—ual Velocâ—ty of Bâ—dies of very dâ—ffeâ—â—nâ— weigâ—ts falling from the same altitude inferred from the same Theâ—â—y Art 18. Gravity Distinguish't into Simple and Adjectitious Art 19. The Râ—â—e of that superlative velocity with which a Bullet would be carried in case it should fall from the Moon Sun or region of the â—ixed stars to the Earth and 〈◊〉 each of those vast heights to the 〈◊〉 of the 〈◊〉 Art 1. What and whence is that Force or Virtue Motive whereby Bodies Projected are carried on after their Dismission from the Projicient Art 2. The Manner of the Impression of that Force Art 3. That all Motion in a free or Empty space must be Vniform and Perpetual and that the chief Cause of the Inequality and Brevity of the motion of things projected through the Atmosphere is the magnetique Attraction of the Earth Art 4. That in the Atmosphere no body can be projected in a Direct line unless perpendicularly Upward oâ— Downward and why Art 5. That the Motion of a stone proâ—ected upwards obliquely is Composed of an Hâ—â—izâ—â—tal and Perpendiâ—ular together Art 6. Demonstration of that Composition Art 7. That of the two different Forces impressed upon a ball thrown upward from the hand of a man standing in a ship that is under sayl the one doth not destroy the other but each attainâ— its proper scope Art 8. Tâ—at the space of time in wâ—iâ—h the â—all is Aâ—cending fâ—om the F 〈…〉 the Top of the Mâ—st is equal to that in which it is again Descending from the top to the â—oot Art 9. 〈…〉 Art 10. The Reason and Manner of the Reflexion or Rebounding motion of Bodies diverted from the line of their direction by others encountring them Art 11. That the â—mersiâ—n of a weight appenâ—â—d to a 〈…〉 the perpendicular 〈◊〉 which it had â—â—duced it self in Vibration 〈◊〉 a Râ—flexion 〈◊〉 betwixt 〈◊〉 Reflexion at all and the Least Reflexion assignable and the Râ—le of all other Reflexion whatever Art 12. â—he â—eaâ—â—n of the Aeâ—ualitâ— of the Angles of Inâ—idenâ—e and Râ—â—lâ—xiâ—n Art 13. Two Inferences from the praeaâ—ses viz. 1 That the oblique Projection of a Globe against a plane is composed of a double Parallel and 2 That Nature suffers no diminution of her right to the shortest way by Reflexion Art 14. Wherein the Aptitude or Ineâ—â—itude of bodies to Refleâ—ion doth consist
the Complexion of any two or more of them But here we are arrested by Two notable and to our praecedent theory seemingly inconsistent PROBLEMS which though of Difficulty enough to deserve the wealthy speculations of Archimedes do yet require from us at least a plausible Solution on the paenalty of no less than the loss of reputation and the posting up a Writ of Bankrupt against our reason by that austere Creditor Curiosity 1 How comes it that those two so discrepant and assymbolical Colours created by a Prism Vermillion and Caerule arise from Causes so Cognate the former only from the Commistion of a greater proportion of Light with a less of Shadows the Later from a less proportion of Light with a greater of Shadows 2 Why when those two Colours Emphatical Vermillion and Carule are by a Prism intermediate projected on a Wall or sheet of white paper beyond it from the light of a Candle if you put your eye in that place â—n which either of the two Colours is appinged so that another person conveniently posited in the same room may behold the same distinctly shining on the pupil of your eye yet shall you plainly and distinctly perceive the other Colour in the Glass For Example if the Vermillion appear on your eye you shall nevertheless clearly see a Caerule in the Glass and transpositively though your eye be manifestly and totally tincted with a Carule yet shall you see a Vermillion Touching the Former we shall adventure to desume the Solution thereof meerly from the Figure of the Prisme and determine the Reason on this only that the Rayes of Light arriving at the Base of the Triangle are trajected through it by a longer tract or way than those arriving at or nearer to the Top thereof and therefore the Glass being in that part most crass there must be more impervious particles obsistent to the Rayes of Light each one whereof repercussing its raye back again into the medium from the Glass causeth that the number of shadowes is multiplyed in that part of the object which the Base of the Triangle directly respecteth and consequently produceth a Caerule Tincture thereon Such as that not only by vulgar but many transcendently learned Heads adscribed to the Firmament which yet belongs rather to that vast many have said infinite Space betwixt it and our Terrestrial Globe being caused by the rayes of the Coelestial Lamps from swarms of minute bodies interposed thinly reflected toward our eyes For each of those impervious particles swarming in that immense space must repercuse a ray of Light deradiated from above and so by multiplying the number of shadows make the Firmament which otherwise according to probability would wear the mourning livery of Midnight appear totally invested in an Azure mantle This though meer Conjecture and indeed the subject is too sublime to admit of other than conjecture since St. Paul hath left us no observation concerning it in his rapture up into the third Heaven and the design of the Ganzaes is desperate hath in it somewhat more of reason then that confident conceipt of Athanas. Kircherus Art Magn. lucis umbrae lib. 1. part 3. cap. 3. de Chromatismis rerum naturalium Medium inter utrumque Caeruleum proximum viz. à nigro seu tenebroso colorem ad jucundissima illa Caelorum spatia inoffenso visu contemplanda Natura providentissima mundo contulit c. that the Providence of the Creator chose this Azure Tincture to invest the Firmament withal as the middle colour between the two Extreams White and Black that so our sight might not when we speculate that universal Canopy be either perstringed with the excessive lustre of the one nor terminated by the absolute opacity of the other Because if the natural Colour of the Firmament were Azure as He praesumes then would it by reason of the vast Space betwixt it and our sight and the repercussion of the greatest part of the rayes of Light from our eye by those Myriads of Myriads of Myriads of small bodies replenishing that intermediate Space necessarily appear of some other colour the experience of Sea-men assuring that all Colours White and that of pure Flame retaining to Whiteness only excepted lose themselves in long trajection through the medium and that even Land which is but few degrees removed from Opacity appears to the first discovery like a blewish Cloud lying level to the Horizon It being certain therefore that by how much the farther any Colour recedeth from Whiteness by so much the less way it is visible which the Graecian intimates in the word 〈◊〉 〈◊〉 〈◊〉 〈◊〉 〈◊〉 Albus 〈◊〉 〈◊〉 〈◊〉 〈◊〉 〈◊〉 quod procul videatur and that even the Earth an Opace body to Sea-men first Kenning it at large distance appears clad in a kind of obscure blewish Mantle it cannot bee dissonant to reason to conceive that the natural Colour of the Firmament cannot be Azure since it so appears to us and that it is rather Opace because it appears Azure when illustrate by the reflected Light of the Coelestial Luminaries Again because the rayes of Light incident on the Top of the Prism are trajected through it by a shorter cut or passage than those incident on the Base and so meet with fewer impervious and retundent particles the Glass being in that part thinnest therefore is the number of shadows much less in that part of the object which respecteth the Cone or Top of the Triangle than in that which confronts the Base and those few shadows which remain undiminisht being commixt with a greater number of lines of light are transformed into the species of a Vermillion Red. Such as that daily observed in the impure Flame of our Culinary Fires which having many particles of Fuligenous Exhalations commixt with its pure luminous particles that continuedly ascending avert as many rayes of light from the eye of the Spectator and so in some degree obnubulate it throughout doth therefore put on the semblance of Redness Or such as the Sun and Moon commonly wear at their rising when the minor part though many of their rayes are reâ—used and averted from our sight by the particles of dense vapours diffused through the spatious Medium However this may be disputed yet is it warrantable to conceive that the superficial Particles of all Bodies clad in either of these Liveries Vermillion and Caerule may have in their Contexture obtained such a Disposition as to reflect Light permixt with small shadows in that definite Temperation or Modification in which it usually arrives at the eye after its Trajection through a Prism when it thereupon impresseth the sense of a Vermillion or Caerule As for the Enodation of the Later Difficulty it is comprehended in the Reasons of the Former For it being certain that the Vermillion projected by a Prisme doth consist of a greater proportion of Light mingled with a less of Shadows and the Caerule on the contrary of a greater proportion of shadows
interspersed among the lines of a less Light and as certain that the Vermillion appeareth on that side of the Prisme where the Light is more copious as therein meeting with fewer retundent impervious particles in the substance of the Glass and the Caerule in that part where the Light is diminished as meeting with more impervious particles and being by them repercussed it must inevitably follow thereupon that if an opacous body be posited within the bounds of this light so that the light may fall on each side thereof and as it were fringe it a symptome quite contrary to the former shall evene i. e. the Vermillion will appear on that side of the species which is over against the Caerule and the Caerule will be transposed to that side of the species which confronteth the Vermillion This is easily Experimented with a piece of narrow black Ribbon affixt longwise to either side of the Prisme For in that case the light is bipartited into two Borders or Fringes the opace part veyled by the Ribbon on each side environed with light and each border of light environed with two shadows or more plainly between each border of shadows conterminate to each extreme of Light trajected through the unopacate parts of the Glass and therefore in the commissure of each of the two lights with each of the conterminous shadows there must be Vermillion on one side and Caerule on the other Now to drive this home to the head the solution of the present Problem the Reason why when the light of a Candle is trajected through a Prism on a White paper or Wall posited at convenient distance beyond it and there transformed into these two luminous Colours Vermillion and Caerule if you put your eye in that place of the Paper or Wall whereon the Vermillion shines you shall perceive only the Caerule in the Glass and è contra we say the Reason of this alteration of site in the Colours seems to be only this that the circumstant Aer about the flame of the Candle being opacous and so serving in stead of two Blacks to environ the borders of light causeth that side of the Candle which is seen through the thicker part of the Glass to appear Blew and that which is seen through the thinner to appear Red according to the constant Phaenomenon in Prismes But if the species be beheld by Reflection from any illustrate and repercussing Body such as the paper or wall then must the series or method of the borders of light and shadow be inverted for the reason immediately praecedent and consequently the situation of the Colours emergent from their various contemperations be also inverted And thus have we by the twilight of Rational Conjecture given you a glimpse of the abstruse Original of the Extreme and Simple Colours and should now continue our Attempt to the discovery of the Reasons of each of those many COMPOUND ones wherewith both Nature and Art so delightfully imbellish most of their peices but since they are as Generally as rightly praesumed to be only the multiplied removes of Light and Darkness i. e. to be educed from the various Commixtures of the Extreme or Simple or both and so it cannot require but a short exercise of the Intellect to investigate the determinate proportions of any two or more of the Simple ones necessary to the creation of any Compound Colour assigned especially when those excellent Rules of that Modern Apelles Albertus Durerus praescribed in his Art of Limning and the common Experience of Painters in the Confection of their several Pigments afford so clear a light toward the remove of their remaining obscurity and the singling out their particular Natures we cannot but suppose that any greater superstructure on this Foundation would be lookt upon rather as Ornamental and Superfluous than Necessary to the entertainment of moderate Curiosity Especially when we design it only as a decent Refuge for the shelter of ingenious Heads from the Whirlwind of Admiration and not as a constant Mansion for Belief For as we cautiously praemonished in the First Article the Foundation of it is not layed in the rock of absolute Demonstration or deâ—umed a Priori but in the softer mould of meer Conjeâ—ture and that no deeper than a Posteriori And this we judge expedient to profess because we would not leave it in the mercy of Censure to determine whether or no we pretend to understand What are the proper Figures and other essential Qualities of the insensible Particles of Light with what kind of Vibration or Evolution they are deradiated from their Fountain What are the determinate Ordinations Positions and Figures of those Reflectent and Refringent particles in the extreams of Bodies Diaphanous and Opace which modifie the Light into this or that species of Colour What sort of Reflection or Refraction whether simple or multiplyed is required to the creation of this or that Colour What are the praecise proportions of shadows interwoven with Light which disguise it into this or that colour Besides had we a clear and apodictical theory of all these niceâ—ies yet would it be a superlative Difficulty for us to advance to the genuine Reasons Why Light in such a manner striking on the superfice of such a body therein suffering such a Reflection or Refraction or both and commixt with such a proportion of shadows in the medium should be transformed into a Vermillion rather then a Blew Green or any other Colour Again were our Understanding arrived at this sublimity yet would it come much short of the top of the mystery and it might hazard a dangerous Vertigo in our brains to aspire to the Causes Why by the appulse of Light so or so modified there is caused in the Eye so fair and delightful a Sensation as that of Vision and why the sentient Faculty or soul therein operating becomes sensible not only of the particular stroak of the species but also of the Colour of it For where is that Oedipus that can discover any Analogy betwixt the Retina Tunica Optick Nerve Brain or Soul therein resident and any one Colour and yet no man can deny that there is some certain Analogy betwixt the Species and Sensory since otherwise there could be no Patibility on the one part nor Agency on the other We are not ignorant that the aspiring Wit of Des Cartes hath made a towring flight at all these sublime Abstrusities and boldly fastned the hooks of his Mechanick Principles upon them thinking to stoop them down to the familiar view of our reason But supposing that all Colours arise from the various proportions of the process and circumvolutions of the particles of Light in bodies respective to various Dispositions of their superficial particles which accordingly more or less Accelerate or Retard them as He hath copiously declared in Dioptric cap. 1. Meteor cap. 8. and erecting this upon his corner stone or grand Hypothesis that Light is nothing but an