about the Sun as Tycho has done we find from his Calculation of it he was fain to allow it a quicker and slower motion in its Orbit to solve the Phaenomena which seems to me but a shift that will serve to help out any lame Hypothesis whatsoever And that granted and the Parallax of the Comet unknown I will undertake very easily to make out almost any Hypothesis which is the fault also of Mr. Horox his Hypothesis wherein he supposes the Earth to be moved about the Sun and the Comet like a Rocket to be shot out of the Sun and by degrees to return to it again in which Hypothesis indeed there seems to be much more reason for an inequality of motion though not in the manner as he has placed it 't was very rational that the motion of it at first if cast out of the Sun should be very swift but then it ought likewise to have accelerated its motion in the same manner in its return back to it again which it does not in his Hypothesis for a stone or any other heavy body being shot up into the Air does make its return back again to the Earth almost by the same degrees of velocity by which it ascended from it almost I say because the resistance of the Air does so far impede the motion of the body through it that it never suffers it to acquire the same degree of velocity with which it was first shot upward This is sufficiently evident from a Pendulum which if it be thrown upwards and be suffered to return back it will never rise again on the opposite side to an equal height with that it descended from on that side towards which it was thrown but besides in his Hypothesis he seems to take no notice at all of the Latitude of the Comet which seemed to carry it much farther off from the Sun when he supposes it to be returning nearer And indeed upon the whole his Hypothesis seems rather a product of chance than of any contrivance For he in endeavouring to set off the Longitude of the Comet according to Tycho's Tables and to trace its way by supposing the Earths annual motion making use always of the same Radius to set off the aspect or apparent angle of it with the Sun his line of Chords he made use of did always direct the point of his Compasses to the place where he situates the Comet as may be easily found by examining the ninth figure where you may find that he places the Comet always equally distant from the Earth and that distance is always equal to the distance of the Sun which has so many inconveniencies and improbabilities that I shall not insist farther on it especially since I do not find that he bestowed any farther pains in explicating or cultivating this his Hypothesis than only the bare delineation of this ninth figure But to return to Tycho's Hypothesis if that be true why did not the Comet again appear after a certain space of time and why could not he have foretold when it should again appear as well as he could predict the appearance of Venus about whose Orb he supposes it to circulate I shall pass by several other very material objections that might be made against that his supposition because many of them might be made also against his Hypothesis of the Heavens in general which I shall the rather omit because I do not find he has many followers in that supposition the generality of Astronomers embracing rather the Copernican System especially as it is refined and rectified by the ingenious Kepler Lastly I endeavoured to trace the way of the Comet from Tycho's Tables according to Keplers Hypothesis which was that the appearances of the motion of the Comet were ascribable to two causes namely the motion of the Earth about the Sun in its annual Orbit and the motion of the Comet in a straight line not accelerated according to the proportion of the increase of Tangents but upon supposition that it mov'd equal spaces in equal times for I cannot imagine what reason he had to suppose its motion to be accelerated and much less why he should assert it to be according to the proportion of Tangents which in a little time must necessarily come to move infinitely swift than which nothing is more hard to be granted And I found it after many trials and essays to fall in a straight line inclining to the plain of the Ecliptick by anangle of 47. 40. and cutting it in 9 degrees of Scorpio if computed out of the Sun and moved faster by half than the Earth in its Orb and this to so great an exactness to answer all the Observations of Tycho that from a very large Scheme which I drew of it on a plain I could never find many minutes difference so that I concluded that to be the most likely Hypothesis for that Comet it seeming to solve all the several Phaenomena of the motion and magnitude of the Comet with the least imaginable difficulty and to be most agreeable with my physical notions of Comets For first it only supposes a solid body moved in a fluid with an almost direct motion I say almost direct because for some physical reasons as I have said before I imagine it not exactly straight but inflected a little towards the curvity of a circle which I shall presently endeavour to explain farther in this Comet Next it supposes that body to move in that line almost equal spaces in equal times I say almost equal because some of those equal spaces may be increased by an accelerating cause or principle such as that of a gravitation towards the body of the Sun placed in the center of its Vortice or System when the motion of the Comet carries it towards the Sun and may be diminish'd from other impeding causes such as the impediment of the fluid medium through which it passes and the attraction of the Sun operating on it when its motion carries it farther and farther off from it besides 't is not unlikely but that the attraction of the Earth or some of the other Planets may have some kind of influence on it especially when its line of Direction does somewhat nearer approach those attractive points But the deflection from a straight line is always so much the less by how much the swifter the body is moved and by how much the farther off its line of trajection is perpendicularly distant from those attracting bodies According to this supposition of mine I have endeavoured to make out all the appearances of this last Comet taken notice of in the best observations I have yet met with amongst which I find no one of the Parallax satisfactory as in the tenth figure let S represent the Sun ORB the Orb of the Earth ACDEF a bended or curve line in which the Comet is supposed to move the Comet then coming into the Sphere of the attractive power of the Sun by the straight
the center of the shining body Next that a Firmament which divided between the waters or the fluids of the one and the fluids of another part of the world And in the third place the collections of particular fluids to one center as the center of the Earth and lastly out of that collection of fluids appeared the dry and solid land So I conceive the most proper way of speculating on these great productions of the omnipotent Creator may be to begin with the consideration of light or the motion of recess from the center of a body Next with the consideration of the cause of the separating of fluid from fluid as Aether from Aether as I may so call differing Aethers because we have not yet distinct names in use and the reason of their conglobation the Aether from the Air the Air from the Water the Water from Quicksilver Oyl or other fluid Thirdly the cause of the conglobating property of each of these fluids when separated how they accept and embrace Homogenea and reject or expel Heterogenea And fourthly how they condense and settle together and produce a solid body whence proceeds the confirmation of attraction or gravitation c. But to digress no further but conclude this part of enquiry in short I suppose the Nucleus or Star of the Comet may be much of the like nature with the central parts of the Earth Moon Mars Jupiter Saturn or other Planets but much impaired in its attractive or gravitating power Next that the Coma or Hazy Cloud about it may be of the nature of the Atmosphere or Air about the Earth or the Smoke or steams about a heated or burning body before they are quite kindled converted into Flame or dissolved into the ambient Air. Thirdly that the Tail or Blaze is much of the nature of the parts of Flame though with those differences I conceive that the parts of these steams are not so close together as are those of Smoke nor doth the motion of them though much swifter upwards than that of our Flame serve to make them appear a shining line but being at that distance they appear much slower to the eye and so discontinue the appearance whence every shining particle appears only a shining point though in the parts of flame where notwithstanding the motion be much flower yet being nearer and so varying the position to the eye much quicker each of the shining parts makes an appearance of a line of light and all of them passing pretty near together make the appearance of a continued fluid flame though that indeed be nothing but a great number of single parcels of the burning body raised up in the particles of Smoke This will appear evident if we consider the appearances easily to be taken notice of in light for 't is obvious from multitudes of experiments that any shining body as a candle or brands end being moved very quick makes the same impression on the eye that a line of light doth standing still And as obvious also that any very light body incompassed with a dark medium appears to the eye under an angle bigger than really it is and a dark body encompassed with a light medium much less This any one may presently find if he make a small hole through a thin plate of metal and holding it first between the light and the eye and so seeing the light appear through it and then placing it so as there is nothing but darkness appears through the said hole for he will plainly perceive that the same hole will appear much bigger in the former position than in the latter Upon this account indeed each of the shining parts of the Comet seems to fill and occupy a much greater space than really it doth and so as 't is observable in the milky way a great number of these small shining bodies though dispersed at a pretty distance one from another yet by reason of the imperceptibleness of each of them they all seem to coalesce into a stream or Blaze of light the brightness of which is yet farther augmented by a clear and unenlightened air and by such a part of the Heaven wherein there appears fewest of the Stars whether they be greater or lesser To the Query Of what magnitude the Body Coma and Blaze of Comets may be No answer can be given until another question be first answered and that is What is the place of Comets and what is their distance from the Earth It was the opinion of most Modern Writers before Tycho Brahe and Kepler I know divers of the Antients thought otherwise that Comets were sublunary Meteors drawn up into the higher Regions of the Air and there set on fire and so continued burning till the Meteor were consumed and as the matter increased or wasted so did the appearance of the Comet But this noble Dane and several others about that time found by accurate observations made that its Parallax was less than that of the Moon and consequently that it was farther distant from the earth that it must be a body of another magnitude and nature than most before that time had imagined and therefore that it ought to be otherwise thought of than the generality of mankind believed concerning it Many had been the attempts of former Writers concerning them to find out their parallax and whether from their unaccurate instruments or from their less skill and diligence in using them or from an imagination of the solidity and impenetrability of the Coelestial Orbs or from error in their calculations or from comparing Observations made at distant places one or both whereof were unaccurate or from a prepossession of Tradition or common Fame or from what other cause soever it were is uncertain but 't was generally concluded by them that all Comets were sublunary Meteors and there are not even at this day wanting some of the same opinion though for what reason I know not 'T will be hard to convince some of these that the opinion they have hitherto received for good is not so because they will hardly give themselves the trouble of examining strictly into the matter And to understand the nature of Parallaxes and how significant they are in determining the distances of bodies from the surface of the Earth to certain degrees thereof beyond which by reason of the imperfections in Instruments and Observations and the exceeding niceness and curiosity necessary they signifie very little It is not my present design to explain what Parallax is that I would suppose my Reader to understand otherwise there can be no reason shewn him to convince him that 't is possible to prove that this or that Comet was not nearer than so many semidiameters of the Earth nor farther off than so many There are then two ways by which we may come to some certainty of what distance a Comet is and those are first the Parallax of its Diurnal motion or its Parallax caused by the Diurnal motion of the Earth And
is taken up into it and kept suspended therein though the parts of the Gold be fifteen times heavier than the parts of the Aqua Regis So Pit-coal though very heavy is yet taken up into the Air and kept suspended therein though it will be found to be some thousands of times more ponderous than the menstruum of the Air that keeps it suspended Many reasons I could produce to shew the great power of the Aether and the universality of its activity almost in all sensible motions but reserving them for another Discourse hereafter I shall at present only mention those suppositions which seem to have the greatest difficulty in this Theory viz. how the dissolution of the parts of the Star by the incompassing Aether should cause light and secondly how it should cause an actual Levitation of the dissolving particles upwards For the explication of these two difficulties I must at present crave favour to explain them by examples taken from operations of Nature in the Atmosphere wherein we live very similar and analogous to them First for the production of light we find that the Air incompassing the steams of bodies prepared by heat or otherwise and made fit for dissolution doth so operate upon them as to make them fly and part asunder with a very impetuous motion insomuch that the small particles or Atoms of the dissolved bodies do not only leave one another but depart and dart out with so great an impetuosity as to drive off all the incompassing Air from their Center from whence they flew and this I take to be the cause not only of their Light but also of their Levity upwards this may be seen very plainly by the small parts of crackling Char-coal which upon the blowing them with Bellows and so crowding a great quantity of the fresh menstruum on them fly and dart asunder with great celerity and noise but is abundantly more evident in the kindling of Gun-powder where the impetuosity is so very great as to drive away not only all the incompassing Air but all other bodies though never so solid that hinder its expansion in the performing of which operation the Aether hath a great share as I may hereafter shew 't is very probable that the Aether in the same manner dissolving the particles of the Star causeth the Atoms thereof to fly asunder with so great an impetuosity as to leave a vacuity even of the parts of the Aether which flying asunder doth not only cause light by impressing on the Aether a stroke or pulse which propagates every way in Orbem but maketh such an agitation of the the Aether as causes a rarefaction in the parts thereof whilst the parts that are once actually separated by continual rebounding one against another before they come to be at rest and quietly to touch each other prolong that first separation or vacuity between them This Explication though it be somewhat difficult yet I hope it is intelligible and may be with probability enough supposed to be the true cause of the appearance whilst there is nothing therein supposed which is not manifestly the method of Nature in other operations and though the supposition even of the Aether may seem to be a Chimera and groundless yet had I now time I could by many very sensible and undeniable experiments prove the existence and reality thereof and that it doth actually produce not only as sensible effects as these I have named but very much the same and many others much more cosiderable which by Philosophers have hitherto been ascribed to quite different causes Had I been able to have made some other observations which I designed if I had had the opportunity of seeing it some of the succeeding Nights I should have hoped to have explained several other difficulties concerning the nature of the body and blaze of Comets but being therein prevented I must leave them till I can make some further observations on some Comets that may hereafter appear In the mean time that what I have discoursed concerning the light of Comets may not seem so altogether paradoxical and unintelligible as some may imagine I have here added an account of some trials and observations made on shining substances of natures exceedingly differing from those that are commonly to be met withal And this I the rather do not only because it affords an instance of shining where there is no Air but that hereby I may enlarge the limits of their imagination who shall consider of this subject For nothing is more apt to misguide our reasoning than a narrow and limited knowledg of causes we are not to conclude the body of a Comet a sulphureous vapour exhaled from the Earth and kindled above because here are such vapours observed and such effects produced nor a collection of Sun beams made by a Lentiformed vapour after the manner of a Burning-glass as some eminent Writers have lately done because some such appearances may be Artificially produced in a smoaky or thickned Air since if we diligently inquire we may find that light which is the most sensible quality of Comets that affects our senses may be and really is produced by very many and those very differing ways In Nitre and Sulphur kindling each other by heat we have one way in a body burning in the Air a second in a heated Iron or Glass a third in a piece of Iron hammered till red hot a fourth in rotten Wood and decayed Fish a fifth in Glow-worms Scolopondras and other living Worms and in the sweat and excrements of other living creatures a sixth in a Diamond rubbed a seventh in Dews Ignes fatui c. an eighth in Sea-water a ninth in the Bononian stone and in the Phosphorus Baldwini which I take to be much of the same nature a tenth in the Phosphorus of Mr. Kraft an eleventh and possibly wholly differing from all these may be the light of the Sun a twelfth and that of the Star may differ from that of Sun and the Comet may be differing from all the rest Whether they be so or not the being acquainted with the several proprieties of them will the better enable one to judg of what is pertinent to be observed in Comets in order to find out which is concerned The Phaenomena of most of these shining bodies are very common and obvious and therefore needless to be added but that of the Bononian stone prepared and that of the Phosphorus Baldwini lately discovered by Mr. Baldwine are rare and hard to be got and the effects of them are wholly differing from all the ways I have yet met with and will therefore prove Experimenta Crucis highly instructive in the Theory of Light of which more hereafter As for the Phosphoros Fulgurans of Mr. Kraft more scarce and rare than the other 't is wholly differing from any of the rest and very strange and surprising at least it appeared so to me who had the good fortune to be present at a good part of
since the appearances may be solved by Circles of any bigness proved by the eighth figure 29. Allowing inequality of motion or more compound curve lines nothing can be determined The circular Orb it seemed the most probable solves Kepler's acceleration according to the increase of a line of Tangents 30. A gravitation towards the Sun makes out the motion of the Comet and Planets and of the Blaze The Blaze explained by experiment of ♂ dissolved in oyl of Virt. 31. This experiment and hypothesis farther explained and applied to explain the Blaze which is from thence bent brighter on one side than the other not direct from the Sun 32. Cometical body and motion as old as the world yet wasting in the Aether explained by fire Dissolution by menstruums 33. Thence the proprieties of Comets conjectured and the sum of the foregoing discourse repeated being the end of a Lecture Recourse to Tycho Brahe's Observation 34. for making out the Comets Orb. His supposing its motion unequal without reason a shift Mr. Horrox his hypotheses in the ninth figure a product of chance 35. A discourse on it and some objections against Tycho's 36. Kepler's hypothesis examined by these Observations of Tycho's found the most likely but with some alteration Line of Trajection bent a little Motion accelerated towards the Sun retarded from it 37. The swifter and further off the Comet from the Sun the less the bend explained by the tenth figure 38. The way of enquiring parallax by Telescopes 39. further explained A second way by two Observers in distant places propounded The third way of Sir Chr. Wren his Majesties Surveyor-General 40. Set down and demonstrated by a Geometrical Problem 41. How exactly all those Observations he had were made out by it together with his own Schemes both which I had in the beginning of Feb. 1664-5 42. Some other Papers about Comets added being reflections on Mr. Descartes and Kepler's hypotheses from particular tracings of the Comets of 1664. and 1665. A Scheme of the later Observations of that of 1664. added and some reflections being all the papers could be found about those Comets 43 44. Animadversions on this of April last Why the former conjectures were adhered to concerning the light of Comets 45. Several sorts of shining bodies enumerated 46 To which the light of the Comet seems to have most affinity and how produced 47. Further described and explained 48. The reason of its parabolick figure demonstrated from the proprieties of motion from or toward a gravitating body as the Sun 49. Concerning the wasting and lasting of the Cometical body The bigness and nature of the Particles that compose the Blaze 50. Some difficulties in this supposition concerning the action of the Aether in levitation and ascent dissolution shining c. cleared and explained by Experiments 51 52 53. But would have been further examined by Observation if there had been opportunity 54. That these assertions about the light of Comets may not seem too paradoxical some further Considerations and Observations about light are added and some new ways propounded 55 56. Mr. Boyle's Memorial concerning a Phosphoros written for his own use inserted in which he first names the Author of it and describes his Apparatus 57 58. Then the observables 1. Two spoonfuls of matter enlighten a large glass sphere 2. A little enlightens a large Cylinder 3. Liquor shaken had a smoke and flasht 4. A dry substance affirmed to have continued shining 2 years flashed 59. 5. Some dust of this on a Carpet twinckled like Stars Writing on paper with it shin'd and smelt of Sulphur and Onions 60. 7. The hand on which it was rubbed shin'd but felt no heat 61. It fired Gun-powder first warm'd 62. And white paper held over coals Other tryals propounded but refused 63. Some Experiments made on the Phosphoros Baldwini in vacuo and in the open air 64. Preserved in Vacuo but destroyed in Air. 65 66. Monsieur Gallet's Letter to Monsieur Cassini acquainting him with his Apparatus for observing ☿ in ☉ 67 68. His Observation of sour spots in ☉ 69. The particulars observed 70. 71 72. Monsieur Cassini's Reflections on these Observations 73 74. Mr. Hally's Letter to Sir Jonas Moore containing an account of his Observations of ☿ sub sole three Southern Stars The two Nubeculae c. 75 76 77. Mr. Cassini's farther discoveries about the diurnal motion and several new appearances in ♃ 78 79 80. A second Discourse called Microscopium or some new discoveries with Microscopes in a Letter of Mr. Leeuwenhoeck 81. 82. A confirmation of some of them by Observations here 83. Mr. Leeuwenhoeck's second Letter containing Observations of the Globules of Blood Milk Flegm Gums first dissolved then precipitated out of the Spirit of Wine Eels a thousand times thinner than a hair 84 85 86 87 88 89. The ways how these discoveries were made here 1. By holding the liquor in small pipes how fill'd how made The Lamp Pipe Oyl Manner Materials for making them described 89 90. Muscovy-glass used instead of these Pipes and how the Microscope was fitted for this purpose 91. What light convenient Surfaces of bodies not perfectly fluid apt to delude an Observer 92. Plates removing that deluding cause and what farther use of them 93. How to find the figure and texture of Animal and Vegetable parts Instance in a ligament of Beef 94. The figure of Muscles hinted and an instrument stretching them before the Glass described 95. A description of the Microscopes used 1. Of the single Microscope and its advantages and difficulties 96. another sort more easie described and the ways how to make and use it explained 97. Causes that vary the distance of objects from the Globule The use of Selenites and Looking-glass-plates for holding the liquor A Microscope of one single refraction 98. The only inconvenience of them hinted how prevented by double Microscopes Where these are made 99. The double Microscope and its parts uses and advantages described 100. The benefit of a dark Room and appropriated lights And a digression in answer to P. Cherubines Accusation 101. Some Observations made with this Microscope hinted Animalcules in the steeping of other Grains besides Pepper Their smallness estimated and compared to a Whale Muscular fabrick hinted Milk Blood Fat Sugar Allum c. viewed 102 103. Mr. Young's Letter of one who trying to cure a Colick by leaden Pills slipt one into his Lungs grievous symptoms ensue 105. Helps of skilful Physicians in vain attempted and particularly of Dr. Mayow of suspending with the head downward though in the interim he married and had Children yet it kill'd him 106 107. His body diffected and remarkables taken notice of and their causes explained by Mr. Young from 107. to 112. COMETA OR Remarks about Comets ON Saturday morning April 21. 1677. I first saw the Comet of which I had been advertised the day before It appeared in the Sign Taurus between the base of the Triangle and the unformed Stars in the
every piece of it though infinitely divided the same proprieties it hath it self This magnetical virtue I say having such a relation and being forced thus to vary 't is very probable that the internal parts to which it hath a respect have a variation likewise and consequently that these internal parts which are supposed generally very dense compact and very closely and solidly united may be notwithstanding more loose and ununited and movable from certain causes To proceed therefore I say that it seems very probable to me that the body of Comets may be of the same nature and constitution with that of the internal parts of the Earth that these parts may by the help of the Aether be so agitated and blended together as to make them work upon and dissolve each other in the same manner as we have often had examples of some of the parts of the Earth a late instance of which was at Mongibel or Aetna in Sicily where the Fire continued for a long time and produced very considerable effects That this internal agitation may confound the gravitating principle and so leave the parts in a greater freedom to be dissolved by the encompassing Aether which is the agent that sets the other two at work to destroy each other that it may at length prey upon both and dissolve them both into it self and consequently not only the parts thus dissolved are elevated to a greater distance from the center of the Star or Nucleus or the superficies of it whose gravitating or attractive principle is much destroyed the Coma being in this Comet four or five Diameters of the Star or Nucleus but having given those parts leave thus far to ramble the gravitating principle of another body more potent acts upon it and makes those parts seem to recede from the center thereof though really they are but as it were left behind the body of the Star which is more powerfully attracted than the minuter steaming parts for I suppose the gravitating power of the Sun in the center of this part of the Heaven in which we are hath an attractive power upon all the bodies of the Planets and of the Earth that move about it and that each of those again have a respect answerable whereby they may be said to attract the Sun in the same manner as the Load-stone hath to Iron and the Iron hath to the Loadstone I conceive also that this attractive virtue may act likewise upon several other bodies that come within the center of its sphere of activity though 't is not improbable also but that as on some bodies it may have no effect at all no more than the Load-stone which acts on Iron hath upon a bar of Tin Lead Glass Wood c. so on other bodies it may have a clean contrary effect that is of protrusion thrusting off or driving away as we find one Pole of the Magnet doth the end of a Needle touched on the opposite part whence it is I conceive that the parts of the body of this Comet being confounded or jumbled as 't were together and so the gravitating principle destroyed become of other natures than they were before and so the body may cease to maintain its place in the Universe where first it was placed Whence instead of continuing to move round some central body whether Sun or Planet as it did whilst it maintained it self entire and so had its magnetical quality as I may so call it unconfounded it now leaves that circular way and by its motion which always tends to a straight line and would be so were it not bended into a curve by the attractive virtue of the central body it flies away from its former center by the Tangent line to the last place where it was before this confusion was caused in the body of it In this line 't is probable it passes from one part of the Heavens to another and so passes through the spheres of the activity of multitudes of central bodies in the passing through which spheres 't is not improbable that those parts which by their dissolution are made of a nature differing from the body in the center are rather expelled from than attracted towards it and so being by this dissolution rarified and loosened from the middle and by their acting upon one another and dissolution of the Aether made of another nature after they have every way dispersed themselves to a considerable distance from their proper body are converted and driven in a way almost opposite to that expelling body and so continue to be driven away to such a vast distance as to make out that prodigious length of the tail or Blaze of some Comets such as was that of 1618. which as Kepler reports was extended to 70 degrees from the body or head of it till at last they are dissolved also and commixed with the Aether within them So that though I suppose the attractive power of the Sun or other central body may draw the body towards it and so bend the motion of the Comet from the streight line in which it tends into a kind of curve whose concave part is towards the Sun by reason that there are some central parts of it which are not yet destroyed and so retain somewhat of its gravitating principle yet I conceive that all those parts of the Comet which are thus wrought upon by the other and changed into another state and are very much rarified and produce light are of a clean contrary nature and recede from the center of the Sun much after the same manner as we find any combustible body with us as Coal c. where we find that the body of the Coal before it be resolv'd into smoke is a very dense and very heavy body and tends to the center of the earth but the parts thereof agitated by the Air and Aether into steams and smoke and those yet farther dissolved into flame do tend upwards and from the center of the earth Now though one cause of the recess of flame from the center of the Earth be the gravity of the ambient Air. Yet 't is not impossible but that there may be somewhat also of positive levity conjoyned therewith Most certain it is that there must be a tendency of receding as well as a tendency of approaching the center of the Earth and other attracting body And there may be much said for the supposition that the recess of the purest Aether from the center is the cause of the motion of the grosser Aether and of all other bodies towards it though there are also very considerable arguments against it But this discourse is not my present business though it may hereafter be the subject of a Lecture in this place for upon it do depend some of the greatest operations in the universe And as in the History of the Creation we have an account of the production of light immediately after the making of matter which is a motion of recess from
sides The Nucleus or Ball in the middle of the head which I have called the Star I conceive to be dissolved equally on all sides and the parts which are dissolved or separated from it I conceive to fly every way from the center of it with pretty near equal celerity or power like so many blazing Granadoes or Fire-balls these continue their motion so far toward the way they are shot till the Levitation from the body of the Sun deflect them upwards or in opposition to the Sun into a Parabolick curve in which Parabolick curve every single particle continues its motion till it be wholly burnt out or dissolved into the Aether These are continually succeeded by new separations from the aforesaid body in the same manner as t is observable in a burning steaming or smoaking body in our air or a dissolving body incompassed with its proper menstruum as I before mentioned and will so continue until the whole be at length dissolved into the Aether through which it passes It hath been demonstrated by Torricellius of bullets or other bodies cast or shot upwards that the same or equal bullets discharged or shot out from the same point with the same degree of strength but with differing degrees of inclination to the Horizon each of them shall be moved in a parabolical line and every one of those parabolical lines shall touch a parabolical line whose axis is the perpendicular and whose apex is distant from the said point the full altitude of the perpendicular shot So that supposing in the twenty second figure A to be the point from whence all the shots are made with equal velocity AC the greatest height of the perpendicular shot and AD the greatest Horizontal random at 45 degrees of inclination and suppose EDCDE a parabola passing through those points DCD all the shots made with equal bullets with equal velocity from A but with all variety of inclination between the perpendicular upwards and the perpendicular downwards that touch the said parabolical line and consequently if there be an indefinite number of such balls continually flowing out of the point A with equal degrees of celerity every way dispersing themselves equally in orbem the whole aggregate of such an emanation will make a solid parabolical conoeid EDCDE Now about the point A if we suppose a Sphere as BBBB and from this Sphere an indefinite number of such equal Balls be thrown off perpendicularly to the superficies of it from every point thereof with equal celerity at their leaving it those emanations will form also a conoeid which will be very near the same with the former And if this Ball in the middle be supposed a burning and shining body and that all these emanations have every one of them equal light in proportion to the Globe BBBBA the effect produced hereby will perfectly resemble the appearance and figure of Comets if at least the Parabolical conoeid be inverted which will somewhat explain the manner how I conceive the figure of the Cometical body is naturally and most proportionably formed for if the effect of such an emanation of shining bodies be examined it will very plainly exhibit the exact and true apparent figure of Comets as they may be seen through a good Telescope which is to me a very great argument that 't is the genuine cause of its shape and figure Now though the Comets appearance be this way caused and so a man might conceive the Globous body would in a little time by so copious an emanation be consumed yet I do not believe that it doth in a short time wast and disperse the whole Ball nor can I conceive that the disappearing of those blazing bodies toward the latter end does depend upon their dissolution though possibly that may somewhat diminish them but that rather is to be ascribed to their distance and position in respect of us Though this I remember I observed very manifestly in that of 1664. that the body toward the latter end of its appearing was very much less in proportion to the radiations about it than it seemed to be at the beginning but whether that might not be partly ascribed to the great distance it then was from us and the turning of the head pretty near towards us and thence the spreading of the Tail appearing beyond it might add to the breadth of the radiation about the Nucleus I will not positively determine Now though for explication sake I have compared the parts separated from the body of the Comet to blazing Granadoes or Fire-balls yet I would not be understood to suppose these parts so separated to be of any very large bulk for I see no necessity to suppose them bigger than the Atoms of smoke or the particles of any other steaming body or than the parts of the Air which make the body of it appear thick and hazy nor do I believe that all the light of the Star head and blaze does depend only upon the shining of the dissolving body and particles thereof but I do suppose that it doth proceed both from the reflection of the Sun-beams from those parts and also from an innate and momentaneous light produced by the action of dissolution wrought on the parts by the incompassing Aether It may possibly seem very difficult to suppose that the dissolution of the parts of the Nucleus by the incompassing Aether should cause or impress so violent a motion into the separated parts as to make them depart from it to the space of four or five Diameters before it be over-powered by the power of Levitation from the body of the Sun and so deflected into a parabolical line upwards It may likewise seem strange to suppose that the Aether should have such power in it as first to dissolve a body into it self and secondly to cause a shining and thirdly to cause a Levitation of the dissolved parts upwards whereas I supposed before and I think 't is very manifest that they cause a gravitation downwards towards the Center of the Sun But to these for explication I answer that we need not go far for instances to make these things probable the Atmosphere about the Earth as I have formerly mentioned in my Micrographia I take to be nothing else but the dissolution of the parts of the Earth into the incompassing Aether for the proof of which I could bring many arguments were it here a proper place by which I could most evidently demonstrate the thing to be as I have asserted It is here evident that this Aether doth take up the particles of bodies to a very great distance from the surface from which they were separated and it doth not only raise them but susteins them at those heights nor is this peculiar only to the Aether when a menstruum but to all dissolving menstruums in general As to give one instance in stead of many we find that Gold the heaviest of all Terrestrial bodies we yet know being dissolved by Aqua Regis
may clearly see such a fabrick as is truly very admirable and such as none hitherto hath discovered that ever I could meet with of which more hereafter when I shew the true mechanical fabrick thereof and what causes its motion Thus if you view a thred of a Ligament you shall plainly see it to be made up of an infinite company of exceeding small threads smooth and round lying close together each of which threads is not above a four hundredth part of the bigness of a hair for comparing those of Beef with a hair of my head which was very fine and small viz. about a 640. part of an inch I found the Diameter thereof to be more than twenty times the Diameter of these threads so that no less than 163 millions besides 840 thousands of these must be in a ligament one inch square I shall not here enlarge upon the admirable contrivance of Nature in this particular nor say any thing farther of the reason of the greater strength of the same substance drawn into smaller than into greater threads but only this in general that the mechanical operations of these minute bodies are quite differing from those of bodies of greater bulk and the want of considering this one thing hath been the cause of very great absurdities in the Hypotheses of some of our more eminent modern Philosophers For he that imagines the actions of these lesser bodies the same with those of the larger and tractable bodies will indeed make but Aristotles wooden hand at best This put me in mind likewise of advertising the Experimenter that he provide himself with instruments by which to stretch and pull in pieces any substance whilst the same is yet in view of the Microscope of which there may be many which any one will easily contrive when he hath this hint given him of the usefulness thereof in the examination of the texture of several substances as of Tendons Nerves Muscles c. those I have made use of were made to open like a pair of Tobacco Tongues by two angular plates of thin brass rivetted together which by pinching the opposite end would either open or shut at the other as I had occasion These having a part extended between the two tops were fixt at a due distance from the object-glass that the body extended between them might be distinctly seen then with my finger squeezing together the opposite ends the other ends opened by which means how the parts stretched and shrunk might be plainly discovered Now as this is of use for some kind of substances so the two glass plates are for others and particularly for squeezing of several substances between them so as to break them in pieces as those little Creatures in pepper-water or the Globules in blood milk flegm c. whereby the parts within them may yet farther be enquired into as Mr. Leeuwenhoeck I find hath done by his latest Observations Whether he makes use of this way or some other I know not Having thus given a description of the appurtenances it remains that I come to the description of the Microscope it self which is the principal instrument and without which all the rest are insignificant The Microscopes then I design here to describe are only of two kinds either single or double The single Microscope I call that which consisteth only of one glass though it have a double refracting superficies and the double one I call that which is compounded of two glasses though it hath for the most part a quadruple refraction of the Rays The single Microscope then consisteth of one small lens so fastened into a cell that the eye may come conveniently to look through the middle part or Axis of it of these there are various sorts as double Convexes or plain Convexes or perfectly spherical I shall not need to describe the common lenses which are every where made use of for this purpose being plano-convexes of Spheres about half an inch Diameter save only this that 't is best to turn the plain side towards the object and the convex to the eye nor shall I say much concerning those double Convex Glasses there being no great difficulty in the making or using of them but that the smaller the sphere is in which they are made the nearer do they bring the object to the eye and consequently the more is the object magnified and the better and truer they are polisht in the Tool the more clear and distinct doth the object appear but to make any of a Sphere less than 1 10 of an inch in Diameter is exceeding difficult by reason that the glass becomes too small to be tractable and 't is very difficult to find a cement that will hold it fast whilst it be completed and when 't is polisht 't is exceeding difficult to handle and put into its cell besides I have found the use of them offensive to my eye and to have much strained and weakened the sight which was the reason why I omitted to make use of them though in truth they do make the object appear much more clear and distinct and magnifie as much as the double Microscopes nay to those whose eyes can well endure it 't is possible with a single Microscope to make discoveries much better than with a double one because the colours which do much disturb the clear vision in double Microscopes is clearly avoided and prevented in the single The single Microscope therefore which I shall here describe as it is exceeding easie to make so is it much more tractable than the double Convex glasses made the common way by working them in a hollow Hemisphere with water and sand for those supposing them made with all the accurateness imaginable will be far short from being so well polisht as these and wanting the stem or handle which these have they are infinitely troublesome to remove or place or to cleanse when there shall be occasion Take then a small rod of the clearest and cleanest glass you can procure free if possible from blebbs sands or veins then by melting it in the flame of a Lamp made with Spirit of Wine or the cleanest and purest Sallet Oyl draw it out into exceeding fine and small threads then take a small piece of these threads and in the same flame of the aforesaid Lamp melt the end of it till you perceive it to run into a little ball or globule of the bigness desired then suffer it to cool and handling it by the aforesaid thread of glass which is as it were a handle to it fix it with a little wax upon the side of a thin plate of Brass Silver or the like that the middle of it may lie directly over the middle of a small hole pricked through the said thin plate with a needle then holding this plate close to the eye look through the said little hole and thereby you may also see very clearly through the aforesaid Globule fixed with wax on the side that is