contrary If I could have seen any Comet to have covered any Star in its way it would have afforded a very circumstantial information especially if for this purpose it had been taken notice of with a good Telescope What the density of the innermost parts of this Earth we live on is none knows for though we find the parts on which we tread to be very compact and though by the industry of Miners it hath been proved so also to the depth of many hundred foot as Georgius Agricola relates and though it hath been found so even to a greater depth by the soundings of the bottom of the Sea yet none can bring an undeniable proof that the same is so solid to 25 miles deep much less that it is so to the center if therefore the external shell of this Globe were broken and removed 't is not impossible but that the middle parts thereof may be of the same nature with the middle parts of the Comets body and that those parts were the superficial parts or shell removed might like these of Comets expand themselves into the encompassing AEther Nay we find that notwithstanding the compactedness of the superficial parts of this Earth yet the AEther is able to take up into it self vast quantities of them and to keep them suspended some of them even to the height of many miles if any argument may be drawn from the height or length of the dawning or Crepusculum and this notwithstanding the attraction of the Earth in its perfect vigor or the gravitation of these parts thus taken up or their endeavour towards the center of the Earth How much more freely then might we imagine the encompassing AEther to prey upon and take up into it self the internal parts if they were of a loose and pervious texture and almost in a state of fluidity like a heap of Sand or a vessel of Alabaster-dust in boyling and were not so firmly united by the bonds of gravity and the vinculum of petrifaction as we find the superficial parts of the earth now are There is one argument to prove to us that there may be such a looseness of the internal parts of the earth and that is that the magnetical virtue varies which virtue without controyersie diffused through the whole body of the Earth and which hath a relation to the whole Globe and to every magnetical part thereof For by observation 't is found that the magnetical virtue acts upon a needle without it as the magnetical virtue of a round Loadstone doth on a Needle applied without that which as I may elsewhere shew hath a respect to the center of the stone differing from all the respects that Authors have hitherto ascribed to it even of Gilbert Kepler Kircher Descartes and our Country-man Mr. Bond who I think was the first man that endeavoured to reduce the variations observed by Wright Gellibrand Coster c. into a Theory and calculation Now this magnetical virtue which may be called one emanation of the Anima mundi as gravity may be called another being diffused through every part of it and seeming to be as it were Tota in toto tota in qualibet parte and to be more spiritual and to act more according to Magical and Mystical Laws than Light Sound or the like it giving to every magnetical body and 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 Load-stone 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 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 slower 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
obvious to any knowing Mechanick and that without the help of Tooth-wheels or Pinions which in works of this nature are in no wise to be made use of by reason of their shaking and uncertainty which I shall elsewhere describe There is one only difficulty in this motion and that is only in such Objects as pass over or very near the Zenith or Nadir of the place for in those cases when the Object comes very near the Zenith the obliquity of the motion of the one to the other is so very great that the first Axis doth not move the second without some difficulty But to remedy this the expedient is as easie and that is by having a little barrel about the perpendicular Arm to carry it forward as far and as fast as the first Inclined axis will permit it which weight may be removed as soon as the Object is a little way past the Zenith The next use that may be made of this is for carrying the Hand of a Clock so as alwaies to move over that point of the Ecliptick in which the Sun is in a Stereographical projection of the Sphere upon the Plain of the Equinoctial or in an Orthographical projection of the said Sphere upon the same Plain so as to express thereby not only the differing right ascensions but the anomaly also of the Suns motion in the excentrick of the Ecliptick And by this means the Face of the Clock may be made by a Planispherical projection to represent the motion of all the Stars appearing in any Horizon that is not too near the Equinoctial their Risings settings culminatings azimuths and almicauters Risings and settings of the Sun the lengths of the Days and Nights and of the Twilights and Dawnings and many other Problems of the Sphere And which is a consequent of this it may be made to shew the equation of Time which is necessary to be made use of for setting a pendulum Clock by the Sun the manner of doing which I must refer to another opportunity as I must also the use of this Joynt for drawing Ellipses drilling and boring of bending Holes for turning Elliptical and Swash-work till I publish my description of a Turning Engine capable to turn all manner of Conical Lines and Conoeidical all manner of Foliage and Flower-work all variety of Basket or Breaded-work all variety of Spiral and Helical-work serving for the imitation of the various forms and carvings of all sorts of Shells for cylindrical and conical Screws all variety of Embossments and Statues all variety of edged and Wheel-like work all variety of Regularly shaped Bodies whether the five Regular bodies of Plato or produced from those by various sections or additions of which the variety is infinite all variety of bended Cylinders or Cones and those whether round in the manner of an Oxes-horn or compressed and angular like those of a Ram or Goat for all manner of Swasht-work Comprest-work c. every of which principal parts hath a vast variety and the compound and decompound principles have a variety almost infinite Appendix Concerning the Eclipse of the Moon observed in London JAnuary the first 167 4 5 being at Sr. Jonas Mores in the Tower of London and making use of a Telescope of eight foot and my pocket-Watch whose ballance was regulated with springs I observed the Eclipse of the Moon which began at about twenty minutes after five the penumbra very much cheating the naked eye for the Penumbra had darkned that side of the Moon next the spot Grimaldi about half an hour before and grew darker and darker towards the edge where the Umbra entred so that if the light of the Moon were diminished either by reflection upon dark Glass or looking through a small hole between a quarter and a third part of the Moon seemed eclipsed before the Umbra entred but the Telescope discovered it plainly to be no true umbra but penumbra This I note because such Persons as do not make use of a Telescope but only of their naked eye are very apt to be much deceived in their estimation of the beginning and end of the Eclipse At 5.48 we judged by the Telescope that the Moon was eclipsed six digits or half at 6.19 the total Eclipse began when the Moon appeared of a very red colour especially towards that part of the Limb where the direct Raies left it which was at the Mare Crisium which is opposite to Grimaldi Now the Skie being somewhat clearer it being before hazy with the Telescope I began to discover a great number of small Stars about the Moon which appeared yet much more conspicuous after I had taken off the apperture from the Object-glass and amongst the rest one seemed very conspicuous and lay in the way of the Moon which I diligently watched and observed that it was just covered by the Moon at 6h. 47′ 30″ the Moon first covering it with that part of it which was almost perpendicularly under the centre of the Moon About three quarters of an hour after the total immersion the body of the Moon was exceeding dark and almost unperceivable being then near the centre of the Umbra and afterwards the Eastermost or foremost part of the Limb of the Moon began to be inlightned whereas before the Westermost Limb had been the brightest This was also very notable that that part of the Moon that was towards the North-Pole a pretty while before the emersion of the Moon out of the total Eclipse and even till the very emersion and somewhat after too appeared inlightned with a much brisker light than any other part of the body except that which was next the Limb where the light again entred From what cause this should happen I know not possibly it might be caused by a greater refraction of the Air near the North-Pole of the Earth and I am much troubled that I had not taken notice whether the like phenomenon had not happened to the body of the Moon before it had past the centre of the Umbra It was very manifest that there was a considerable quantity of light that kept that Limb of the Moon which was next the light conspicuous by the Telescope all the time of the total Eclipse and 't is very rational to ascribe it to the Raies of the Sun refracted by the Air or atmosphere of the Earth I was very well pleased to observe the Moon to cover several small Stars that lay in its way but I kept no account of them but only watched diligently when the Star that entred behind the Moon at 6.47.30 would come out again which I found it to do at 7 30′ seeing it at the very moment of time that it began to appear again And it was also at the same instant discovered by Sr. Jonas More who was expecting it with another Tube At 7.58 the body of the Moon first emerged out of the Umbra at the spot Grimaldi and soon after all those small Stars that were
the best of all is Quicksilver because it doth not with keeping evaporate at all sensibly which I have carefully observed for these fifteen years last past Nor doth it grow thick or foul by the alteration of the Air nor do I find it sensibly alter by the heat and cold at lest not comparable to the great changes which other Liquors suffer by the alterations of those qualities It is an excellent material for measuring time in a standing Machine and there may be hundred of ways contrived to make it measure the space thereof as accurately as a Pendulum and I have many times admired that Tycho Brahe who was otherwise so curious and exact in the contrivance and make of his Engines and Instruments was yet so defective in his contrivances of measuring time by Quicksilver when there were so many obvious and easie ways of doing it as he seems to complain in his works I have made trial of several with very good success and found some of them even beyond expectation certain of which I may hereafter upon an other occasion add the descriptions when I publish the various ways of making exact Time-keepers or Watches In the mean time being now speaking of Time-keepers for variety sake I shall mention A New Principle for Watches THis is a way of regulating both standing Watches and movable Watches either for the Sea or the Pocket which some ten or twelve years fince I shewed the Royal Society when I shewed them my contrivances of the Circular Pendulum which is since published by Monsieur Hugenius which is also mentioned in the History of the said Society p. 247. lin 20. This was by a fly moving Circularly instead of a ballance whose motion was regulated by weights flying further and further from the Center according as the strength of the Spring of the Watch had more and more force upon its Arbor The Weights were regulated from flying out further than they ought to do by the contrivance of a Spiral Spring drawing both the said Weights to the Center of the motion or fly in the same proportion as I then demonstrated Gravity to attract the weight of a Circular Pendulum moved in a Parabolical Superficies towards the Center or Axis of its motion The Weights were so contrived as always to counterpoise each other The Skeleton of this fly you have represented in the Figure The particular explanation of the parts and the Geometrical Demonstration of the Principle both of the Springs and of the flying from the Center I shall explain in the Theory of Springs and in the description of Time-keepers and Watches 〈◊〉 〈◊〉 〈◊〉 〈◊〉 〈◊〉 Arist Quaest Mechan An Observation about the Seed of Moss SInce the publishing of my Micrography I have met with an Observation which though it be of one of the smallest compound bodies I have hitherto taken notice of yet does it afford a hint of very great concern in Natural Philosophy And it does seem to make clear the cause of a Phaenomenon that hath appeared dubious not only to me but to many other more knowing Naturalists I have often doubted I confess whether Moss Mushroms and several other small Plants which the Earth seems to produce 〈◊〉 〈◊〉 〈◊〉 〈◊〉 〈◊〉 were the off-spring of a Seed or Grain and I have been apt to believe that they were rather a secondary production of Nature being somewhat the more inclined to that opinion because having formerly examined the small knots or Seed-cods of Moss with a single Microscope I could not perceive any thing in them that I could imagine to be Seed at least not so great a quantity as seemed necessary to maintain so numerous a Progeny as was every where to be found of it that which then came out of them seeming to be rather a pulp or pith than any thing like the Seeds in other similar Cods But being since somewhat more inquisitive I did examine several of the above-mentioned Knobs or Seed-vessels and found that there were seeds in them no less wonderful for the greatness of number than the smalness of bulk Taking then some of the ripe and brown or reddish ones of them and pressing them pretty hard I found that there was a small dust went out of them which seemed to vanish into the Air. Pressing and squeezing others of these upon a black-plate and examining the powder with a Microscope I found it to be a great heap of exceeding small Seeds Globular and pretty transparent It is the smallest I confess I have yet seen and it may be that has hitherto been discovered And unless that be a plant which I discovered growing on the blighted leaves of Roses and that those small bodies be seed vessels or unless those Knobs I have discovered on the top of mould be the like I cannot presently imagine where there should be found a smaller For I find that there will need no less than thirty six hundred of them to be laid one by another in a line to make the length of an Inch and to cover the Superficies of an Inch-square there will need no less than nine hundred and threescore thousands besides twelve millions of single Seeds if laid quadrangularly but if laid triangularly there will need no less than two hundred and fourscore thousand besides seventeen Millions of single grains And the number in a grain weight of them cannot be less than one thousand three hundred eighty two Millions and four hundred thousand single grains about eighty of these square Superficies of Seeds being laid one upon another in the Trigonal order making as near as I can guess the thickness of a piece of fine Paper a square Inch of which weigheth a grain And though this may seem a most incredible narration yet I would desire such as are apt to be too censorious to take the pains to gather a few of these Seed-vessels and examine them as I have done and then speak what they find and believe no more than their own sense and reason will inform them and they may easily see that what I have asserted will be rather short of than exceed the real numbers Now if this Shell of the Seed be thus small how much smaller must needs be the rudiment of the Plant that lies enclosed within it And how easily may such Seeds be drawn up into the Air and carried from place and place even to the tops of the highest Towers or to places most remote and be sowed by the passing Air or falling drops of Rain on the boughs or branches of Trees sides and tops of Walls Houses or Steeples And it is not in the Art of man to leave Earth exposed to the common Air and to exclude the entrance or prevent the sowing of these imperceptible Seeds and therefore it is not to be wondred at that if any earth though never so pure be exposed to the Air and Rain though at the top of a Steeple it will produce Moss Further inquiry may possibly instruct us that there
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 four 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 dissected 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 Cloud of Aries dignified by P. Pardies with the figure of the Flower-de-luce The head of it was in a right line with the heart of Cassiopea and Alamak or the South foot of Andromeda and as near as I could judge by my naked eye having no Instrument or help by me it was ⅚ of the distance between the feet and the Girdle of Andromeda distant from the said Alamak towards the South It s tail sometimes as the Air was clearer and darker extended about three quarters of its distance from the aforesaid Alamak and pointed directly at the Star in the nose of Cassiopea of the fourth Magnitude and consequently the head of the Comet pointed not directly at the Sun the Sun then being about the eleventh degree of Taurus but rather towards the fourteenth degree of the same Sign It s appearance was very small and slender and as people commonly ghessed about two yards long and the head about the bigness of a Star of the first magnitude but of a much fainter and duller light It s blaze about three o' the clock seemed to rise straight upward before that about half an hour after two it leaned a little Eastwards or towards the right hand and after three as it rose higher inclined towards the left side or Westwards The head to the naked eye was brighter than the blaze and seemed to be somewhat bigger than that part of it which immediately joyn'd to the head but those parts of it which were farther distant were of a much greater breadth spreading wider and wider as they were more remote from the head and in the same proportion also growing fainter and fainter in their light especially towards the outsides but the middle parts or medulla appear'd much longer and the brightness much greater which made the whole blaze to seem to taper or be pointed towards the top The length of the Blaze appeared sometimes shorter and sometimes longer by several vicissitudes and as the day-break or dawning increased so the Blaze shortened and especially towards the sides near the top and shortly after before the Sun rose disappeared But notwithstanding this shortning and lengthening of the Blaze I could not perceive any kind of motion in the parts of it such as is observable in flame smoke or other steams rising from a burning or hot body but the same parts of the Blaze seemed to appear and disappear in their proper places as if they had been fixed and a solid body The first Figure I have here annexed will with some short explications represent the appearance of it to the eye more plainly than by a multitude of words without it 't is possible to express A represents the head of the Comet the middle of which appeared brighter than any other part about which was a hazy light somewhat like the shining of a Star through a thin cloud the lower part of which was pretty round and defined B the neck of it which seemed to the naked eye of less Diameter and less bright than the head but through a six-foot glass as I shall mention by and by it appeared bigger though not so bright The middle of this was very bright and seemed to issue from the Nucleus or Star in the middle of the head C the brushy parts which were fainter and paler towards the sides especially nearer the top which made the whole seem to taper and resemble the Figure here exprest Observing it with Telescopes one of which was fifteen foot and the other six foot long I found the shape of it much like this which I have represented in the second Figure It had a pretty bright Star if I may so call it near the middle
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 deslection 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 O R B the Orb of the Earth A C D E F 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 line P A G at A the power of the Sun worketh on it and by degrees attracting it towards its own Center by that time the Comet hath moved to C the attractive power hath deflected its direct course from P A G to C H and so the Comet would continue to move in that straight line C H but it is still deflected so that at D it moves towards I but the gravitation of the Sun attracting it deflects it from that line towards E and so from E to F when it begins again to Jet out of the attractive beams of the Sun and so it will continue to proceed as if it had come to that point by the line M F L the reason of which is the great velocity of these bodies which are generally much swifter in their motions than the Earth or other Planets are supposed to be in theirs We must seek out some other way therefore of finding of the distance of Comets than the commonly used I shall therefore somewhat further explain the contrivance I newly invented for this purpose by which not only the Parallax of the Comet but of the Planets also may be found with great facility and exactness Having a large Telescope prepared as I formerly directed with Eye-glasses capable of taking in an Angle of about two degrees at once and furnished with a dividing Scale observe when the motion of the Comet or Planets is not too fast the position and distances of the small fixed Stars which are next adjoyning to the moved body whose Parallax you would find of these small fixed Stars you shall seldom miss a sufficient number which will be taken into the glass at once if at least the object-glass be allowed a very large aperture and having found such Stars as will be convenient for your purpose be very diligent in taking by the help of the dividing Scale the exact distance of them one from an other and when the body is highest above the Horizon viz. in or near the Meridian by the same means take the exact distance of it from two or three of the nearest and most conspicuous fixt Stars about it and by the help of a plumb-line hung likewise within the cell near the dividing Ruler find exactly the positions of all those bodies you take notice of to the Perpendicular or Horizon which may be easily enough done if together with a Plumb-line or Perpendicular plac'd within the glass you have also a small Diagonal thred fastned to a ring whose circumference is divided into 360 degrees and moveable so as by the finger easily to be turn'd any way by which means this Diagonal thred may be made to cross over any two of the bodies you observe and by observing what division of this divided limb the Perpendicular cuts it will be easie to determine the exact position of those Stars to the Horizon this same may be done by the dividing Scale also if that be fixt in a divided Circle which is movable in the same manner as the thred is supposed to be This Observation with all other circumstances of it is likewise to be repeated at the setting or rising of the Planet or Comet and again the next night when it comes to the Meridian and in each of those observations the exact time is to be noted by a time-keeper and the altitude by some of those I have before described for by comparing these three observations together it will be very easie to find what
susceptible of a much more subtil impulse even from light it self as the Bononian stone and Bladwines Phsophorus which seems to be so harmonious as I may so speak to the motion of light that a new motion is thereby raised in it and continues for some time to move of it self after the impulse or influence ceases not much unlike the unison string or other sounding body which in Musick receives a tremulation and sound from the motion and sound of the unison body or string that is struck To me It seems most probable that the body and parts of the Comet are in a state of dissolution whether that dissolution be caused by the parts of the Aether through which it passes after the manner as a Torch is dissolved by the air or whether by the internal working of the constituent parts one upon the other as in Gun-powder shining Fish and rotten Wood I cannot determine but I rather guess it to be in some things analogous to the one and somewhat to the other though not exactly the same with either And this I conceive from the figure and make of the shining parts for if it had been of the same nature with a Torch the blaze would have resembled that of the flame of a Torch or Candle that is the sides would have been brighter and the middle darker as I have shewn in my Lampas whereas it was very manifest that the middle of the blaze was brightest and of that blaze that which was next the Star or Nucleus was brighter than that which was further off whereas in flame the contrary is very observable as I have in the said Treatise shewn From the shape of the figure the manner of its dissolution seems to be thus The Star or Nucleus in the middle seems to be the fomes or source from whence all the light proceeds this we suppose to be a dense body encompast with a very fluid body such as the Aether seems to be but of such a loose and spongy nature as that the Aether doth cause those parts which are contiguous to it to be dissolved and expanded into it self This dissolution and expansion I conceive doth generate or cause the light that seems to proceed from it that dissolution causing such a motion of the Aether as is necessary to produce the appearance of light now so long as any part thereof remains in dissolution so long doth it continue to shine as is also observable in the flame of any body burning in the air but when the part separated from the body is quite dissolved into the Aether the effect of shining ceases as it doth also in the parts of flame Now I have observed that the blaze is so very much rarified that first the Aether I conceive comes very freely to every particle of the body after it is separated from it but especially to the outermost and continues to be incompassed with it so long as till it be quite dissolved into it which I conceive to be at a little farther distance from the head than the greatest length of the blaze seems to be to our sight And further I conceive that the outward parts being thus incompassed more perfectly with the free and undisturbed Aether are sooner dissolved into it than those of the middle and consequently the sides seem first to disappear and the middle parts continue their shining to a much greater distance from the Star in the head though somewhat also of that appearance may be ascribed to the dispersing and rarity of the parts near the 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 A C the greatest height of the perpendicular shot and A D the greatest Horizontal random at 45 degrees of inclination and suppose E D C D E a parabola passing through those points D C D 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 E D C D E. Now about the point A if we suppose a Sphere as B B B B 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 B B B B A 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 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
rather than instruct him especially of such substances as are not perfectly fluid and will not readily and naturally smooth their own superficies such as Tallow concreted Oyls Marrow Brains Fat inspissated juyces c. for if those substances be so examined by spreading them upon this plate and be looked upon against the candle or other small defined light all the inequalities left on the surface by the spreading do by the refractions of the rays of light render such odd appearances that they will easily deceive the examinator and make him to conceive that to be in the texture of the part which is really no where but in the make of the superficies of it This therefore as another great inconvenience to be met with in Microscopical Observations I prevent by these ensuing methods First all such bodies as Fat Oyl Brains Rhobs Pus tough concreted Flegm and the like whose surfaces are irregular and ought to be reduced to smoothness before they can be well examined I order in this manner First I provide a very clear and thin piece of looking-glass plate very smooth and plain on both sides and clean from foulness upon the surface of this I lay some of those substances I last mentioned then with such another piece of Looking-glass plate laid upon the said substance I press it so thin as not only to make the surfaces of it very smooth but also to make the substance of it very thin because otherwise if the substance be pretty thick as suppose as thick as a piece of Venice paper if it be a whitish substance the multitudes of parts lying one upon another in such a thickness do so confound the sight that none of them all can be distinctly seen but if by squeezing the said plates hard and close together it be reduced to a twentieth part perhaps of that thickness the substance may be well looked through and the constituent parts may be very plainly discovered Thus also 't is very visible in the Globules of milk and blood discovered by the ingenious Mr. Leeuwenhoeck for when either of those substances are thick the multitude of those little Globules confound and thicken the liquor so as one cannot perceive any thing until it be run very thin for then all the remaining Globules with their motions may very distinctly be apprehended This therefore is an expedient by which thousands of substances may be examined and therefore the more fit to be communicated that there may be the greater number of observers well accommodated for such trials These plates therefore may be contrived so as to be pinched together by the help of screws and a frame that thereby they may be forced the closer and the evener together as there shall be occasion and may be kept firm and steady in that posture and then that it may some ways or other be conveniently fastned to the former plate so as to be moved this way or that way steadily as there shall be occasion But there are other substances which none of these ways I have yet mentioned will examine and those are such parts of animal or vegetable bodies as have a peculiar form figure or shape out of which if it be put the principal thing looked after is destroyed such are the Nerves Muscles Tendons Ligaments Membranes Glandules Parenchymas c. of the body of Animals and the Pulps Piths Woods Barks Leaves Flowers c. of Vegetables Some of these which are not made by dissection or separation from other parts may be viewed alone but there are others which cannot be well examined unless they be made to swim in a liquor proper and convenient for them as for instance the parts of flesh muscles and tendons for if you view the fibres of a muscle encompassed only with the air you cannot discover the small parts out of which it is made but if the same be put into a liquor as water or very clear oyl you 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
minute of time their motion being of such a Velocity impressed from the Ambient on the two extreme Particles 1 and 8. First if by any external power on the two extremes 1 and 8 they be removed further asunder as to CD then shall all the Vibrative Particles be proportionably extended and the number of Vibrations and consequently of occursions be reciprocally diminished and consequently their endeavour of receding from each other be reciprocally diminished also For supposing this second Dimension of Length be to the first as 3 to 2 the length of the Vibrations and consequently of occursions be reciprocally diminished For whereas I supposed 1000000 in a second of the former here can be but 666666 in this and consequently the Spring inward must be in proportion to the Extension beyond its natural length Secondly if by any external force the extreme particles be removed a third part nearer together than the external natural force being alway the same both in this and the former instance which is the ballance to it in its natural state the length of the Vibrations shall be proportionably diminished and the number of them and consequently of the occursions be reciprocally augmented and instead of 1000000 there shall be 1500000. In the next place for fluid bodies amongst which the greatest instance we have is air though the same be in some proportion in all other fluid bodies The Air then is a body consisting of particles so small as to be almost equal to the particles of the Heterogeneous fluid medium incompassing the earth It is bounded but on one side namely towards the earth and is indefinitely extended upward being only hindred from flying away that way by its own gravity the cause of which I shall some other time explain It consists of the same particles single and separated of which water and other fluids do conjoyned and compounded and being made of particles exceeding small its motion to make its ballance with the rest of the earthy bodies is exceeding swift and its Vibrative Spaces exceeding large comparative to the Vibrative Spaces of other terrestrial bodies I suppose that of the Air next the Earth in its natural state may be 8000 times greater than that of Steel and above a thousand times greater than that of common water and proportionably I suppose that its motion must be eight thousand times swifter than the former and above a thousand times swifter than the later If therefore a quantity of this body be inclosed by a solid body and that be so contrived as to compress it into less room the motion thereof supposing the heat the same will continue the same and consequently the Vibrations and Occursions will be increased in reciprocal proportion that is if it be Condensed into half the space the Vibrations and Occursions will be double in number If into a quarter the Vibrations and Occursions will be quadruple c. Again If the conteining Vessel be so contrived as to leave it more space the length of the Vibrations will be proportionably inlarged and the number of Vibrations and Occursions will be reciprocally diminished that is if it be suffered to extend to twice its former dimensions its Vibrations will be twice as long and the number of its Vibrations and Occursions will be fewer by half and consequently its indeavours outward will be also weaker by half These Explanations will serve mutatis mutandis for explaining the Spring of any other Body whatsoever It now remains that I shew how the constitutions of springy bodies being such the Vibrations of a Spring or a Body moved by a Spring equally and uniformly shall be of equal duration whether they be greater or less I have here already shewed then that the power of all Springs is proportionate to the degree of flexure viz. one degree of flexure or one space bended hath one power two hath two and three hath three and so forward And every point of the space of flexure hath a peculiar power and consequently there being infinite points of the space there must be infinite degrees of power And consequently all those powers beginning from nought and ending at the last degree of tension or bending added together into one sum or aggregate will be in duplicate proportion to the space bended or degree of flexure that is the aggregate of the powers of the Spring tended from its quiescent posture by all the intermediate points to one space be it what length you please is equal or in the same proportion to the square of one supposing the said space infinitely divisible into the fractions of one to two is equal or in the same proportion to the square of two that is four to three is equal or in the same proportion to the square of three that is nine and so forward and consequently the aggregate of the first space will be one of the second space will be three of the third space will be five of the fourth will be seven and so onwards in an Arithmetical proportion being the degrees or excesses by which these aggregates exceed one another The Spring therefore in returning from any degree of flexure to which it hath been bent by any power receiveth at every point of the space returned an impulse equal to the power of the Spring in that point of Tension and in returning the whole it receiveth the whole aggregate of all the forces belonging to the greatest degree of that Tension from which it returned so a Spring bent two spaces in its return receiveth four degrees of impulse that is three in the first space returning and one in the second so bent three spaces it receiveth in its whole return nine degrees of impulse that is five in the first space returned three in the second and one in the third So bent ten spaces it receives in its whole return one hundred degrees of impulse to wit nineteen in the first seventeen in the second fifteen in the third thirteen in the fourth eleven in the fifth nine in the sixth seven in the seventh five in the eighth three in the ninth and one in the tenth Now the comparative Velocities of any body moved are in subduplicate proportion to the aggregates or sums of the powers by which it is moved therefore the Velocities of the whole spaces returned are always in the same proportions with those spaces they being both subduplicate to the powers and consequently all the times shall be equal Next for the Velocities of the parts of the space returned they will be always proportionate to the roots of the aggregates of the powers impressed in every of these spaces for in the last instance where the Spring is supposed bent ten spaces the Velocity at the end of the first space returned shall be as the root of 19. at the end of the second as the Root of 36. that is of 19+17 at the end of the third as the Root of 51. that is of 19+17 +15. At the end of the