Lectiones Cutlerianae OR A COLLECTION OF LECTURES PHYSICAL MECHANICAL GEOGRAPHICAL ASTRONOMICAL Made before the Royal Society on several Occasions at GRESHAM Colledge To which are added divers MISCELLANEOUS DISCOURSES By ROBERT HOOKE S.R.S. LONDON Printed for John Martyn Printer to the Royal Society at the Bell in S. Pauls Church-yard 1679. The Titles of the several TRACTS I. AN ATTEMPT to prove the Annual MOTION of the EARTH by Observations made with accurate Instruments wherein is shewn the Impossibility of doing it by the most exact Instruments and ways used by preceding Astronomers The Instruments and method used in these Observations The way of seeing the fixed Stars in the Day time and a new Hypothesis for solving the motions of the Heavenly Bodies is hinted II. ANIMADVERSIONS on the Machina Coelestis of Mr. Hevelius wherein is detected the imperfection of Astronomical Instruments hitherto used and divers ways of reforming and perfecting those and several other Instruments are explained and described And several other new Inventions are added and explained as particularly Water-Levels The Circular Pendulum the Perfection of Wheel-work for Clocks and Watches c. together with their uses and the great advantage of these above other Inventions of the like nature III. A DESCRIPTION of Helioscopes with other Instruments Wherein are Discovered and Described several new ways of making Glasses to look upon the Body of the Sun without offence to the Observers Eye 2. A shortning Reflective and Refractive Telescope 3. A way of using a Glass of any length without moving the Tube 4. An Instrument for taking the Diameter of the Sun Moon and Planets or other small Distances in the Heaven to the certainty of a Second 5. An Instrument for describing all manner of Dials by the Tangent Projection 6. The uses of the said Instrument First for adjusting the Hand of a Clock so as to make it move in the shadow of a Dial whose Stile is parallel to the Axis Or Secondly in the Azimuth of any Celestial Body that is in the shadow of an upright or any other way inclining style upon any plain Thirdly for making a hand move according to the true Aequation of Time Fourthly for making all manner of Elliptical Dials in Mr. Foster's way c. Fifthly for communicating a circular motion in a Curve Line without any shaking And for divers other excellent purposes To which is added an Observation of the Eclipse of the Moon Jan. 1. 167 ◠5. And a Postscript concerning the Invention of regulating Watches by Springs applyed to their Ballances together with a Decade of other useful Inventions part discovered part described in Anagrams IV. LAMP AS or Descriptions of some Mechanical Improvements of Lamps and Water-poises with other Physical and Mechanical Discoveries Wherein are discovered besides the ways of obviating the inconveniencies of other contrivances of Lamps Eight several ways of making Lamps so as to regulate the flame of them for various uses several of which are therein mentioned and explained Besides which various ways and uses are described of poysing liquors by the by several Theories and Explications are inserted particularly about Flame and Burning about Light Colour Gravity Local Motion Pressure of Fluids c. in Answer to some Objections of Dr. More against some former Discourses published by the Author To these are added the Description of a new sort of Clepsydra or Water-Clock 2. A new Principle for regulating Pocket Watches 3. Several Microscopical Observations about the Seeds of Mosse Mushrooms all kinds of Ferns Wall-Rue Harts-Tongue Osmund Royal c. 4. An Observation of spots in the Sun V. COMETA containing Observations on the Comet in April 1677. Also for the years 1664. 1665. Sir Christopher Wren's Hypothesis and Geometrical Problem about those Comets A Discourse concerning the Comet 1677. Mr. Boyl's Observation made on two new Phosphori of Mr. Baldwin and Mr. Craft Mr. Gallet's Letter to Mr. Cassini together with his Observation of ☿ sub ☉ Mr. Cassini's Reflections upon those of Gassendus and Hevelius and upon this Mr. Hally's Letter and Observation of the same made at St. Helena Mr. Cassini's Observation of the Diurnal motion of ♃ and other Changes happening in it MICROSCOPIUM containing Mr. Leeuwenhoecks two Letters concerning some late Microscopical Discoveries The Author's Discourse and Description of Microscopes improved for discerning the nature and texture of Bodies P. Cherubines Accusations Answered Mr. Yonge's Letter containing several Anatomical Observations VI. LECTURES de Potentia Restitutivâ or of Spring Explaining the Power of Springing Bodies To which are added some Collections viz. A Description of Dr. Pappins Wind-Fountain and Force-Pump Mr. Yong's Observation concerning natural Fountains Some other Considerations concerning that Subject Capt. Sturmy's Remarks of a Subterraneous Cave and Cistern Mr. G. T. his Observations made on the Pike of Teneriff Anno 1674. Some Reflections and Conjectures occasioned thereupon A Relation of a late Eruption in the Isle of Palma AN ATTEMPT To prove the MOTION OF THE EARTH FROM Observations MADE BY ROBERT HOOKE Fellow of the Royal Society Senec. Nat. Qu. lib. 1. cap. 30. Nè miremur tam tardè erui qua tam altè jacent LONDON Printed by T. R. for John Martyn Printer to the Royal Society at the Bell in St. Pauls Church-yard 1674. TO THE TRULY HONORABLE Sir John Cutler KNIGHT and BARONET My Worthy PATRON SIR AMong several Eminent Marks of your Greatness of Mind for promoting the Publick Good that of your Bounty for the Advancement of Experimental and Real Knowledge by the Founding a Physico-Mechanical Lecture deserves to be Recorded as One and more especially by me whom you have honoured by establishing your first Lecturer As an Earnest of others more considerable shortly to follow I here present you with one of my Discourses in that Employment which though short and plain conteins somewhat of Information which the Learned have hitherto desired though almost with despair As I hope their kind Acceptance will produce their thanks to you to whom they are justly due so your Acceptance will incourage me in the further prosecution of these Inquiries to approve my self Noble Sir Your most obliged and most humble Servant ROBERT HOOKE From Gresham Colledge March 25. 1674. READER I Have formerly in the Preface of my Micrographia given the World an account of the founding a Physico-Mechanical Lecture in the Year 1665 by Sir John Cutler for the promoting the History of Nature and of Art In prosecution thereof I have collected many Observations both of the one and the other kind and from time to time as obliged I have acquainted the Royal Society at their Publick Meetings both at Gresham Colledge and Arundel House therewith by Discourses and Lectures thereupon Now in order to the further promoting the End and Design of this Lecture I have complyed with the desire of several of my Friends though otherwise not thereunto obliged to commit divers of those Discourses to the Publick though of themselves for
of this supposed annual motion of the Earth about the Sun as its center though moved in an Orb whose Diameter is by the greatest number of Astronomers reckoned between 11 and 12 hundred Diameters of the Earth Though some others make it between 3 and 4 thousand others between 7 and 8 and others between 14 and 15 thousands and I am apt to believe it may be yet much more each Diameter of the Earth being supposed to be between 7 and 8 thousand English miles and consequently the whole being reduced into miles if we reckon with the most amounting to 120 millions of English miles It cannot I confess but seem very uncouth and strange to such as have been used to confine the World with less dimensions that this annual Orb of the Earth of so vast a magnitude should have no sensible Parallax amongst the fixt Stars and therefore 't was in vain to indeavour to answer that objection For it is unreasonable to expect that the fancies of most men should be so far streined beyond their narrow dimensions as to make them believe the extent of the Universe so immensly great as they must have granted it to be supposing no Parallax could have been found The Inquisitive Jesuit Riccioli has taken great pains by 77 Arguments to overthrow the Copernican Hypothesis and is therein so earnest and zealous that though otherwise a very learned man and good Astronomer he seems to believe his own Arguments but all his other 76 Arguments might have been spared as to most men if upon making observations as I have done he could have proved there had been no sensible Parallax this way discoverable as I believe this one Discovery will answer them and 77 more if so many can be thought of and produced against it Though yet I confess had I fail'd in discovering a Parallax this way as to my own thoughts and perswasion the almost infinite extension of the Universe had not to me seem'd altogether so great an absurdity to be believed as the Generality do esteem it for since 't is confessedly granted on all hands the distance of the fixt Stars is meerly hypothetical and not founded on any other ground or reason but fancy and supposition and that there never was hitherto any Parallax observed nor any other considerable Argument to prove the distances supposed by such as have been most curious and inquisitive in that particular I see no Argument drawn from the nature of the thing that can have any necessary force in it to determine that the said distance cannot be more then this or that whatever it be that is assigned For the same God that did make this World that we would thus limit and bound could as easily make it millions of millions of times bigger as of that quantity we imagine and all the other appearances except this of Parallax would be the very same that now they are To me indeed the Universe seems to be vastly bigger then 't is hitherto asserted by any Writer when I consider the many differing magnitudes of the fixt Stars and the continual increase of their number according as they are looked after with better and longer Telescopes And could we certainly determine and measure their Diameters and distinguish what part of their appearing magnitude were to be attributed to their bulk and what to their brightness I am apt to believe we should make another distribution of their magnitudes then what is already made by Ptolomy Ticho Kepler Bayer Clavius Grienbergerus Piff Hevelius and others For supposing all the fixt Stars as so many Suns and each of them to have a Sphere of activity or expansion proportionate to their solidity and activity and a bigger and brighter bodied Star to have a proportionate bigger space or expansion belonging to it we should from the knowledge of their Diameters and brightnesses be better able to judge of their distances and consequently assign divers of them other magnitudes then those already stated Especially since we now find by observations that of those which are accounted single Stars divers prove a congeries of many Stars though from their near appearing to each other the naked eye cannot distinguish them Such as those Stars which are called Nebulous and those in Orion Sword and that in the head of Aries and a multitude of others the Telescope doth now detect And possibly we may find that those twenty magnitudes of Stars now discovered by a fifteen foot Glass may be found to increase the magnitude of the Semidiameter of the visible World fourty times bigger then the Copernicans now suppose it between the Sun and the fixt Stars and consequently sixty four thousand times in bulk And if a Telescope of double or treble the goodness of one of fifteen should discover double or treble the said number of magnitudes would it not be an Argument of doubling or trebling the former Diameter and of increasing the bulk eight or twenty seven times Especially if their apparent Diameters shall be found reciprocal to their Distances for the determination of which I did make some observations and design to compleat with what speed I am able But to digress no further This grand objection of the Anti-copernicans which to most men seem'd so plausible that it was in vain to oppose it though I say it kept me from declaring absolutely for the Copernican Hypothesis yet I never found any absurdity or impossibility that followed thereupon And I alwayes suspected that though some great Astronomers had asserted that there was no Parallax to be found by their observations though made with great accurateness there might yet be a possibility that they might be mistaken which made me alwayes look upon it as an inquiry well worth examining first Whether the wayes they had already attempted were not subject and lyable to great errors and uncertainties and secondly Whether there might not be some other wayes found out which should be free from all the exceptions the former were incumbred with and be so far advanced beyond the former in certainty and accurateness as that from the diligent and curious use thereof not only all the objections against the former might be removed but all other whatsoever that were material to prove the ineffectualness thereof for this purpose I began therefore first to examine into the matter as it had already been performed by those who had asserted no sensible Parallax of the annual Orb of the Earth and quickly found that whatever they asserted they could never determine whether there were any or no Parallax of this annual Orb especially if it were less then a minute which Kepler and Riccioli hypothetically affirm it to be The former making it about twenty four Seconds and the latter about ten For though Ticho a man of unquestionable truth in his assertions affirm it possible to observe with large Instruments conveniently mounted and furnished with sights contrived by himself and now the common ones for Astronomical Instruments to the accurateness of
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 sire 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 secondly the Parallax of its proper motion compared with the Periodick or Annual motion of the Earth The first of these may be observed two ways either by two Observers at parts of the Earth very far distant from each other but as near as may be under the same Meridian as suppose the one in London the other in St. Helens both conspiring in their observing of the place of the Comet amongst the fix'd Stars at the same time Or secondly by one Observer in the same place by observing the place of it amongst the fix'd Stars in its rising or setting and in a greater or if it may be its greatest height The noble Tycho by very accurate Observations of the Parallax proves the Comet of 1577. to be above the Moon Kepler by his own Observations proves that of 1607. at its beginning to be four times farther distant and I doubt not but some may have been above forty times farther But I do not yet find that any Observations have accurately determined that which is indeed the great help by which we are inabled to judge of the nature and all the other accidents and proprieties of Comets The Aristotelian Philosophy for a long time prevailing made the world believe them to be nothing but Exhalations from the Earth drawn up into the higher Regions of the Air. But Tycho by his Observations of their Parallax raises them out of that confinement but yet he seems to place them in an Orb about the Sun But Kepler frees them from that confinement and assigns them the Universe to expatiate in But none of all these do accurately prove the true distance of them their Parallax being for the most part so very small that I fear Instruments with common lights will hardly reach them But we must expect from future observations made with Telescopical Instruments to receive a certain Answer to this Query Certain I am that the Comet which began to appear in November 1664. and disappear'd in March following was far removed beyond the distance assigned by Kepler For by my own Observations divers times repeated I could not find any senfible Parallax though I endeavoured by a new method to make my Observations more accurate Now though I had not the convenience of making use of a Quadrant or any such Instrument to observe its place when near the Horizon yet the way I took would I think be as good which was this With a very good six foot Perspective-glass or Telescope I observed the place of the Comet in respect of the adjacent small Stars as soon as it appeared and so traced its way till it disappeared in the vapors of the Horizon the like I did several other days successively taking notice by what degrees in what times it made its progress to see whether by its Parallax when near the Horizon it would have been deprest below that line of its motion which it kept when at a greater height above it But though I tried this several times yet I was not able to discern that the Parallax of it caused either any sensible bending of the line or any sensible inequality in its progress by which I should have sooner found it than by taking its altitudes with common Instruments though I confess these Observations were made when the motion of the Comet was slow and consequently when in probability it was far distant from the earth To me there seems no doubt but that it was a long way removed above the Moon when I made these Observations for had it been of an equal distance with that they allow the Moon it must this way have manifested a very sensible
it But as to the third I hope the indefatigable labour and skill of Monsieur Hevelius will shortly supply the present defect though it had been much to be wish'd that the Instruments he had made use of had been fitted with Telescopical sights These Tables if well done will alone as to the business of Comets at least supply the place of all other Instruments almost save only a thread especially if they be so delineated in Tables after the Tangent projection as that the minutes of every degree may be very distinguishable which will not swell the Maps of the Heavens into an extraordinary large volume and may possibly be the cheapest Instrument for this purpose an Astronomer can be furnished withal for having such a volume of Tables it will be very easie with a thread and one's eye screen'd only with a spectacle made of a thin plate of Brass with a small hole through it instead of a glass to observe what place the Comet possesseth amongst the fixt Stars for having by the help of the said thread observed what two Stars lie in the same line with the Comet on one side of it and what other two Stars lie in a line with it which is at right angles as near as may be with the former line by finding out those four Stars in the Tables ordered according to the Tangent projection and with a Ruler drawing lines over them respectively where those lines do intersect there will be the true place of the Comet from which it will not be difficult to find out the true Longitude and Latitude of it by a Sector with Tangents Now as these Tables of all the fixt Stars visible to the naked eye would serve for finding its place whilst very big and swift of motion so the like Tables of the small Telescopical Stars that lie near its way when almost disappearing and moving very slow will by the help of a pair of measuring Compasses placed within the eye-glass of the Telescope and a straight line or hair drawn cross it serve to find the true motion and way of it when only visible with a Telescope according to which method I made the annexed Schemes and Observations of the last appearances of the Comet Now since neither from my own nor from any other Observations that I have hitherto met with there can be any certain conclusion drawn of the distance of these Comets save only this that their distance was very great and much higher than the body of the Moon because else there must have been a considerable Parallax caused by the Diurnal motion The next enquiry will be what other ways there are of knowing its distance Now though none could be more demonstrative than the Parallax found this way by the Diurnal motion yet there are some other which seem more easie arising from the consideration of the motions that may be thought to be concern'd in the producing the appearances And though they be wholly hypothetical and so need some other arguments to prove the ground and principles on which they are founded yet since there are not very many considerable ones wanting to make them probable and rational I shall here add somewhat of my inquiries after the distance position motion magnitude c. of these Comets by these means Of these ways there are several depending upon several suppositions which produce very differing effects as to the magnitude distance motion and way of the same Comet The suppositions are these Either that the Earth moves in an annual orb about the Sun as the Sun is supposed by others to move about the Earth Or that the Earth is perfectly fix'd and hath no such motion Next that the Comet moves either in a straight line or in a curve line and the curve is either a circle or some other regular or irregular curve Further that the motion of the Comets in these lines is either by equal or unequal spaces in equal times Now according as we take this or those of these differing suppositions and compound them together so will the product of them be strangely differing Amongst the great variety of compositions of these principles or suppositions these seem the most simple and consequently being any otherwise proved will best determine the true distance and way of the Comet First To suppose the Earth to stand still and the Comet to move equal spaces in equal times in a circle Secondly To suppose the Earth to move in an annual Orb about the Sun and the Comet to move through the Aether or Expansum equal spaces in equal times in a straight line Thirdly To suppose the Earth to move as above in its annual Orb and the Comet also to move equal spaces in equal lines in a circle The other are indeterminate and infinite and nothing can be concluded from them as to the distance magnitude motion c. of Comets for the line or way of the Comet may be placed at any distance if we will suppose it moved in an uncertain curve with unequal degrees of velocity And indeed upon a supposal of an inequality of motion nothing of its way or distance can by any of these suppositions be found out This fault had that of Tycho Brahe where he supposed an unequal motion of it in its Orb about the Orb of Venus which was founded upon the first Hypothesis but had introduced into it some inequality of motion besides his own supposition that it was moved about the Sun and the Sun about the Earth See the fifth Figure Keplers way which was after the second Hypothesis had the same fault for he supposed the annual motion of the Earth and the motion of the Comet in a straight line but introduces an acceleration of motion in the Tangent towards the latter end The third way I have here taken and from the best observation I could meet with I have delineated its respects or angles to the Sun and accordingly supposing it to move equal spaces in equal times in a curve which for so much of it as the Comet was observed to pass was very near a Circle I found this Circle would fall as it is express'd in the seventh Figure where 't is obvious to take notice that when the Comet was nearest to the Earth namely about the 19. or 20. of December that it was not nearer than an eleventh part of the distance of the Sun that on the 23 it was twice as far that on the 29. it was four times as far that on the 15. of January it was as far as the Sun and on the 14. of February it was above twice as far distant as the Sun That this way or Orb of the Comet is here bended so as if it were an entire Circle one part of it would go without the Orb of Jupiter as the other which is here delineated comes within the Orb of the Earth that the plain of this Orb is inclined to the plain of the Ecliptick about 18 degrees that if
from several parts this Orb perpendiculars be let fall upon the Plain of the Ecliptick those perpendiculars shall fall in an Ellipsis part whereof shall fall within the Orb of the Earth in ♌ and the opposite without the Orb of ♃ ♒ That the Comet moves a Sextant of this Orb in about 130 days and consequently if its motion should continue the same in such a Circle it would appear about February March or April 1667. but being so far removed towards the South Pole will here hardly be seen but by those that live towards the South it may appear to have some such motion by the South Pole as that of 1618. had by the North. And 't is not impossible but that the Comet of 1618. might be the same with this if we suppose the Nodes of it to have a motion contrary to the order of Signs and that the same Node which in this Comet according to this supposition was in ♊ was then about ♠or ♠but these as conjectures I shall not insist on because neither in this nor in that have we Observations sufficiently accurate to build any Theory upon Now though upon these suppositions the motion and appearances of the Comet seem to be very regularly and very naturally made out yet 't is not the only Hypothesis for that design nor do I believe it so evident a demonstration for that end as some would suppose though for other reasons I am apt enough to think that opinion of the Earths motion very probable but the motion of this Comet is so well made out by the contrary supposition that I think it may be alledged for a greater argument against the motion of the Earth than for it for if we only grant one of the former postulata namely that the body of the Comet is moved equal spaces in equal times and a quite contrary postulatum to the former namely that the Earth remains fix'd as to an annual motion we may find all the observations of this Comet especially the most accurate of them to happen so that the Comet being supposed to be moved in a great Circle whose convex side is turned towards the Earth whose center is extended towards the fix'd * in ♋ and whose Semidiameter is about sixscore times the nearest distance of the Comet from the Earth and the Comet be supposed to be moved very near equal spaces in equal times we shall find I say all the appearances most exactly solved and indeed much more exactly than by the other supposition I was able to find any for by this supposition both the magnitude longitude latitude retrogradation station and direction of the Comet is most exactly made out as any one might have found that should have by this means examined with me the observations I have hitherto either made or met with and indeed all the Observations hitherto have so well answered this Hypothesis that I do almost promise my self to be able to see this Comet a month or six weeks hence after the Sun has past by it if by its exceeding elongation it be not quite grown out of sight as it is now indeed already so exceeding dim and faint that it cannot be seen without a very good glass which will endure an exceeding big aperture nor could I these two last nights perceive it though the Air were clear but the reason I attribute to its nearness to a fixed * of ♈ This Hypothesis is explained in the seventh Figure By this supposition the return of the Comet will be much longer and the time of seeing of it much more uncertain because the curvature is so little that the making the circle a twentieth or a sixteenth part bigger or less does not much alter the regularity whence 't is exceeding difficult unless we had much more accurate Observations than I have hitherto met with to determine exactly the bigness of the circle and consequently the time of the return And by this supposition the Comet may be supposed either nearer or farther from the Earth at any distance which is not contradicted by a Diurnal Parallax that is it may be supposed either above Saturn or below the Moon or in any place between by supposing only that the farther the nearest part of the Circle is distant from the Earth the greater must that Circle be and the swifter the motion of the Comet in it to prove which affirmation let in the Eighth figure A be the Earth BCD the Orb of the Comet supposed very near the Earth and E F G the Orb of it supposed at a greater distance let H be the center of B C D and I of E F G and let A C be to C H as A F to F I all the lines drawn from the point A so as to cut the Circles B C D and E F G shall divide those Circles E F G and B C D into similar segments as let A B E be a line drawn cutting those Circles in B and E I say the Arch B C shall be similar to E F. In which Hypothesis if we have together with the place of the Comet when stationary the place of it when in its greatest celerity perige or the places of it when of the same celerity on each side of its perige we have from thence the proportion of the Radius of its Orb to the perigean distance and consequently all the other distances the line in which it appears when stationary being the Tangent to the Circle in which it moves as A B E to which a Perpendicular raised at B B E and produced till it cut the line A C produced at H H I it gives the Center of its Orb H H I and the proportions of the lines A B AC B H = H C or of A E A F E I = F I the Angle B A C being given by observation So that by this Hypothesis the Phaenomena of the motion and bigness of the Comet will be solved though supposed of any distance Nor are these the only Hypotheses by which the hitherto observ'd Phaenomena may be solv'd for if we will admit an unequal motion such as is now granted to all the Planets and if further we will admit it to be moved in an Elleipsis or other such like curve there may be divers other Hypotheses that will solve the Phaenomena so that the Comet may be supposed to have no motion at all as to Longitude but only as to Latitude that is it may be supposed to be moved in an Elleipsis described in a plain which shall be at right Angles with the plain of the Ecliptick and the ways of the Earth in it it may be supposed also to have been mov'd direct according to the order of the signs that is to have been first about Gemini in respect of the Sun and to be now in some part of Leo And it is not impossible to solve the phaenomena of its periodick or proper motion though it be supposed not so high as
irregularity in its motion is ascribable to its Parallax And this will be so much the easier because the examination and reduction of it may be done with as great exactness as the observation can be made by the help only of Ruler and Compasses for all the distances will be set off by equal divisions of straight lines the line also of the periodick motion whether of the Comet or Planet especially if the observations be made when the body is near an opposition with the Sun which is much the best time will be with sufficient exactness taken for a straight line and the motion in that line may be supposed by equal spaces in equal times for the difference between the Tangents of the centesms of a degree to two degrees is not increased much more then 2 1745 that is not a quarter of a centesm of the hundredth part of a degree which is much more exact than I fear our observations will ever be Another way of finding the Parallax may be by the help of exact observations made by several persons at the same time in places much differing in Latitude though as near as may be under the same Meridian because of saving the trouble of Calculation and for being assured that the observations were both made exactly at the same time each person by the help of very long Telescopes observing the exact distance of the body from the small fixt Stars next adjoyning A third way of finding the Parallax of Comets is wholly new and though hypothetical as supposing the annual motion of the Earth and the motion of the Comet in a right line through equal spaces in equal times yet 't is founded upon a Problem in Geometry invented by the incomparable Mathematician Doctor C. Wren which is truly noble and wholly new and though it had been of no use in Astronomy deserves none of the meanest places in Geometry by the help of which which is much more than either of the other ways is capable of one may easily find the true parallax of the Comet from any four exact observations of it made at differing times in the same place Nor does it require so nice and accurate Instruments and Observators as are altogether necessary in the other ways The Problem as I received it is this Problema Datis quatuor lineis utcunque ductis quarum nec tres sunt parallelae neque ab eodem puncto ductae quintam ducere quae à quatuor primo datis in tres partes secetur ratione positione datas Sint in Figuris 13 14 15 16 17 18 quatuor rectae ADC BEC AE BD productae versus K γ φ M oportet quintam ducere ut KM quae secetur à primo datis in segmenta KN NO OM secundum datas rationes R S T. Fiat ut R ad S T simul sumptas ita CD ad CF. Rursus ut T ad S R simul sumptas ita EC ad CG ductis autens AGH BFH à mutua intersectione H ducantur H γ K H φ M parallelae nimirum lineis AC BC quae mediae interjacent inter extremas BD AE Denique inter puncta extremarum KM ducatur Recta secans medias in NO Dico segmenta KN NO OM esse in Data ratione RST Quoniam FD parallela est ipsi HK ergo ut CD ad CF ita K γ ad γ H quoniam γ N parallela est ipsi HM ergo ut K γ ad γ H ita KN ad NM ergo ut KN ad NM ita CD ad CF sed CD ad CF est ut R ad S T simul sumptas ergo KN est ad NM ut R ad ST simul sumptas Similiter quoniam EG parallela est ipsi MH φ O ipsi HK demonstratur MO esse ad OK ut T ad S R simul sumptas Quare tres KN NO OM erunt ad invicem ut R S T ergo ducitur linea KM cujus tria segmenta à quatuor lineis datis intercepta sunt in data Ratione R S T servata quidem positione sive rationum ordine R S T quod erat faciendum From the invention of which Problem 't will be very easie by any four observations Graphically to describe or Geometrically to calculate the true distance of the line of the trajection of the Comet and consequently to answer all those questions that can be demanded concerning the bigness of the body and head and concerning the bigness and length of the blaze and concerning the distance of it from the Earth in every part of its way when it was nearest the Earth when nearest the Sun where it cuts the Plain of the Ecliptick seen from the Sun and where seen from the Earth with what Angle it was inclined to the said Plain how swift the motion was that is what length it passed in what time when it must appear Stationary when Retrograde when disappear and the like According to this method I received at the same time whilst it yet appeared very visible to the Eye and was not Retrograde the way of the first Comet delineated by the said person which did very near solve all the appearances preceding and subsequent which I have therefore here annexed in the Table expressed in the 19.20 and 21. figures where in the 19. is delineated the Place of the Sun in the Center of the Circle ♈ N D I ♎ which represents the annual Orb of the Earth about the Sun the points between N and D represent the places of the Earth in that Orbit in the days of November and the lines drawn from them to the points in the straight line represent the lines in which the Comet appeared in respect to the Sun in like manner the points between D and I the places of the Earth in December and the lines drawn from them to the straight line as before the visible places of the Comet at those times c. The 20. figure represents singly the several Longitudes of the Comet at several times seen from the Earth And the 21. represents the several Latitudes at the several times together with the true distances of the Comet at those times both which are made out of the 19. figure where E at the end of the line represents the Center of the Earth from which to the figures in the prickt curve-line are the true distances of the Comet the Perpendiculars from those figures to the line E C are the signs of the Latitude of the Comet from the plane of the Ecliptick E C the aforesaid distances being made the Radii Now though according to my former Delineation the Comet seemed to take a circuit as if it would within three years return to its former position yet I am not wholly convinced that it moves in a circle or Ellipse but I rather incline to the incomparable Keplers opinion that its natural motion tends towards a straight line though in some other suppositions I differ from him As first that the Comet
of the Glass stood North. Then I change the side of the Object Glass and put the North side Southwards and the South Northwards and observe the Transitus of the same Star the next night and note down the same the third night following I put the East side or E North and observe the transit of the same Star over the Meridian and the fourth night I put the West side or W North and observe the transit of the said Star Now by comparing all these together it will be very easie to deduce what the false refraction of the Object Glass is and which way it lyes and consequently to regulate the apparent Zenith by the true one But this only by the by 'T is manifest then by the observations of July the Sixth and Ninth and that of the One and twentieth of October that there is a sensible parallax of the Earths Orb to the fixt Star in the head of Draco and consequently a confirmation of the Copernican System against the Ptolomaick and Tichonick Before I leave this Discourse I must not forget to take notice of some things which are very remarkable in the last observation made upon the 21 of October And those were these First that about 17 minutes after three a-clock the same day the Sun being then a good way above the Horizon and shining very clear into the Room where I lay to observe and having nothing to screen off the rayes of light either in the Room where I was or in the next Room through which I looked I observed the bright Star in the Dragons head to pass by the Zenith as distinctly and clearly as if the Sun had been set though I must confess it had lost much of the glaring brightness and magnitude it was wont to have in the night and its concomitants were vanisht The like I found it divers other dayes before when I observed it the Sun shining very cleer into both the aforesaid Rooms which by the way I suppose was the first time that the fixt Stars were seen when the Sun shin'd very bright without any obscuring of its light by Eclipse or otherwise And though we have a great tradition that the Stars may be seen with the naked eye out of a very deep Well or Mine in the day yet I judge it impossible and to have been a meer fiction without any ground For the being placed at the bottom of a Well doth not at all take away the light of the Atmosphere from affecting the eye in and near the Axis of vision though indeed the sides thereof may much take off the lateral rayes but unless the radiation of the false rayes of the Star be brighter then that of the Air the true rayes from the body are so very small that 't is impossible the naked eye should ever be affected by them For in the second place by this observation of the Star in the day time when the Sun shined with my 36 foot Glass I found the body of the Star so very small that it was but some few thirds in Diameter all the spurious rayes that do beard it in the night being cleerly shaved away and the naked body thereof left a very small white point The smalness of this body thus discovered does very fully answer a grand objection alledged by divers of the great Anti-copernicans with great vehemency and insulting amongst which we may reckon Ricciolus and Tacquet who would fain make the apparent Diameters of the Stars so big as that the body of the Star should contain the great Orb many times which would indeed swell the Stars to a magnitude vastly bigger then the Sun thereby hoping to make it seem so improbable as to be rejected by all parties But they that shall by this means examine the Diameter of the fixt Stars will find them so very small that according to these distances and Parallax they will not much differ in magnitude from the body of the Sun some of them proving bigger but others proving less for the Diameter of the parallactical Circle among the fixt Stars seems to exceed the Diameter of the Star almost as much as the Diameter of the annual Orb of the Earth doth that of the Sun And possibly longer and better Telescopes will yet much diminish the apparent bulk of the Stars by bringing fewer false rayes to the eye that are the occasion of the glaring and magnifying of the said bodies It may for the present suffice to shew that even with this Glass we find the Diameter of this Star considerably smaller then a Second and the Parallax we judge may be about 27 or 30 Seconds It will not therefore be difficult to find many Stars whose Diameters shall be less then a two hundredth part of this Parallax as possibly upon more accurate observation this very Star may be found to be Now we find that the Diameter of the Orb of the Earth is but two hundred times bigger then the Diameter of the Sun in the Center thereof and therefore if the parallactical difference be found to be two hundred times more then the visible Diameter of the Star the Star will prove but of the same magnitude with the Sun This Discovery of the possibility and facility of seeing the fixt Stars in the day time when the Sun shines as I think it is the first instance that hath been given of this kind so I judge it will be a discovery of great use for the perfecting Astronomy as first for the rectifying the true place of the Sun in the Ecliptick at any time of the year for since by this means 't is easie to find any Star of the first second or third magnitude at any time of the day if it be above the Horizon and not too near the body of the Sun And since by a way I shall shortly publish any Angle to a Semicircle in the Heavens may be taken to the exactness of a Second by one single observator It will not be difficult for future Observators to rectifie the apparent place of the Sun amongst the fixt Stars to a Second or very near which is one hundred times greater accurateness then has hitherto been attained by the best Astronomers The like use there may be made of it for observing any notable appulse of the ☽ ♃ ♄ ♂ and ♀ to any notable fixt Star that shall happen in the day time which may serve for discovering their true places and parallaxes The Refractions also of the Air in the day time may by this means be experimentally detected I should have here described some Clocks and Time-keepers of great use nay absolute necessity in these and many other Astronomical observations but that I reserve them for some attempts that are hereafter to follow about the various wayes I have tryed not without good success of improving Clocks and Watches and adapting them for various uses as for accurating Astronomy compleating the Tables of the fixt Stars to Seconds discovery of Longitude
Springs according to the modern Hypothesis though all here concurred did notwithstanding fail of producing that effect From the same it is also manifest that where Springs fail without want of the causes that Hypothesis supposeth necessary to produce them the occasion hath been from an apparent defect in the other that is the imperviousness of the earth through which the water must pass before a Spring can be produced both these appeared at Lipary where the general effect a Spring or fountain was wanting together with the causes of our Hypothesis though those of the other were manifestly existent and with all the advantages necessary It seeming to me a very rational conjecture that the greasie clammy Sulphur wherewith that earth was impregnated did by oppilating it hinder the insinuation of the Sea into it From the third observation you have the first deduction confirmed viz. That Springs are sometimes manifestly from the Sea That earth sweetens Sea-water by Percolation And that the nearer Springs are to the Sea the more they retain of their pristine saltness and lose it by sensible degrees as they insinuate farther through it By the fourth the same is confirmed The fifth proveth that large streams flow without any possibility of being supplied by rain both for want of such rain and of dimensions to receive and contain it The sixth doth evidence that rain doth not penetrate the Surface of the earth even in a very dry parched Country and in the Torrid Zone and yet that Springs are under it which at once proves ours and refutes the other opinion the former appears by the water in those made Ponds lying there for a long time without any sensible loss thereof by its leaking into the earth The later by the Wells near the Sea and those found since under that impervious Land He that is not altogether a stranger to the weight pressure and Elasticity of the air the ascension of liquors through Filters and some other resembling Phaenomena would not account the like motion of the transcolated water to high hills to be an objection of any force against this Hypothesis but sure such solutions are no less beyond my ability than design Finding I have Paper enough left I will presume to trouble you with one rare appearance more that occurred to one Mr. Brasey of this Town and aged and very fat man who by taking Spirit of Vitriol in his mornings draughts to which he was advised as a remedy to asswage the exuberance of his belly found that it had no effect on his body but that a bundle of Keys which he used to carry always about him and that wonted to be very smooth and bright of a sudden became black and rusty though he never handled the Spirit nor carried it in his pocket so that we concurred in opinion that the sudorous Effluvia of his body impregnated with the Acid Spirit had occasioned it If so It 's very wonderful that so small a quantity thereof when diluted with so much juice as is contained in such a corpulent man should even insteam and the insensible Emanations make impressions on smooth Iron mauger the perpetual attrition by carrying them in his Pocket whereby such an effect one would think should be prevented or soon rubbed of I was going to make some reflections on this notable accident but I consider c. Plimmouth May 5. 1678. James Young THE Original of Springs is that which hath exercised the Pens of many learned Writers and very various have been the conjectures concernning it But amongst all I have met with I conceive none more probable than that which seems to fetch its original from the History of the Creation mentioned in Holy Writ that is that there is a Magazine of waters above as well as a Receptacle of waters upon or beneath the Surface of the Earth And that the Air is that Firmament which separates between the upper and lower waters and between these two is the circulation of waters or bloud of the Microcosm if I may so call it performed The water being sometimes by a particular constitution of the Air assisted by heat rarified and separated into minuter parts and so reduced into the form of Air and thereby being divided into Particles really smaller than those of the air in compassing and agitated with a greater degree of motion they take up more space and so become lighter than the Ambient and are thereby elevated and protruded upwards till they come to their place of poise or Equilibrium in the Air At other times by a differing constitution of the Air and deficiency of heat they lose their agitation and many of them again coalesce and so having less motion they condense and revert into water and so being heavier than the incompassing Air descend down again to the Earth in Mists Rain Snow Hail or the like That there is such a Circulation I think there is none doubts but still it remains a difficulty with those persons that grant this that all Rivers and Springs should have their original from the water that falls or condences out of the Air. To persuade such persons it may not possibly be unsuccessful to mention First That the great inundations or overflowing of Rivers manifestly proceed either from the Rain that immediately falls or from the melting of Snow or Ice that hath formerly fallen on the more eminent parts of Mountains to confirm which Histories enough might be brought were it necessary of Nilus Niger c. Secondly That it hath been observed and computed that communibus annis locis there falls water enough from the Sky in actual Rain Snow or Hail upon the Surface of England to supply all the water that runs back into the Sea by the Rivers and also all that may be supposed to evaporate nay though the quantity of the first be supposed twice as much as really it is This I have been assured by those that have both experimented and calculated it Thirdly That there is not yet certainly that I know or have heard of any other way of making salt water fresh but by Distillation which had there been such an Art it would in all probability have been made use of and so there is little probability that the Springs at the top of a high Hill should proceed from the Sea-water strained through the earth But were there such a filtration known I hinted in my Attempt published anno 1660 about Filtration how somewhat of that kind might be explained Fourthly That this Operation is constantly and most certainly performed by Nature both in exhaling and drawing up fresh steams and vapours from the Sea and all moyst bodies and in precipitating them down again in Rain Snow Hail but of the other we have no certainty Fifthly I have observed in several places where a Tree hath stood upon an high Hill singly and particularly at the brow of Box Hill near Darking in Surry that the body of the Tree is continually wet and at
therewith who have confined their imaginations fancies only within the compass and pale of their own walk and prospect who can scarce imagine that the Earth is globous but rather like some of old imagine it to be a round plain covered with the Sky as with a Hemisphere and the Sun Moon and Stars to be holes through it by which the Light of Heaven comes down that suppose themselves in the center of this plain and that the Sky doth touch that plain round the edges supported in part by the Mountains that suppose the Sun as big as a Sieve and the Moon as a Chedder Cheese and hardly a mile off That wonder why the Sun Moon and Stars do not fall down like Hail-stones and that will be martyr'd rather then grant that there may be Antipodes believing it absolutely impossible since they must necessarily fall down into the Abyss below them For how can they go with their feet towards ours and their heads downwards without making their brains addle To one I say thus prejudiced with these and a thousand other fancies and opinions more ridiculous and absurd to knowing men who can ever imagine that the uniformity and harmony of the Celestial bodies and motions should be an Argument prevalent to perswade that the Earth moves about the Sun Whereas that Hypothesis which shews how to salve the appearances by the rest of the Earth and the motion of the Heavens seems generally so plausible that none of these can resist it Now though it may be said 'T is not only those but great Geometricians Astronomers and Philosophers have also adhered to that side yet generally the reason is the very same For most of those when young have been imbued with principles as gross and rude as those of the Vulgar especially as to the frame and fabrick of the world which leave so deep an impression upon the fancy that they are not without great pain and trouble obliterated Others as a further confirmation in their childish opinion have been instructed in the Ptolomaick or Tichonick System and by the Authority of their Tutors over-awed into a belief if not a veneration thereof Whence for the most part such persons will not indure to hear Arguments against it and if they do 't is only to find Answers to confute them On the other side some out of a contradicting nature to their Tutors others by as great a prejudice of institution and some few others upon better reasoned grounds from the proportion and harmony of the World cannot but imbrace the Copernican Arguments as demonstration that the Earth moves and that the Sun and Stars stand still I confess there is somewhat of reason on both sides but there is also something of prejudice even on that side that seems the most rational For by way of objection what way of demonstration have we that the frame and constitution of the World is so harmonious according to our notion of its harmony as we suppose Is there not a possibility that the things may be otherwise nay is there not something of probability may not the Sun move as Ticho supposes and the Planets make their Revolutions about it whilst the Earth stands still and by its magnetism attracts the Sun and so keeps him moving about it whilst at the same time ☿ and ♀ move about the Sun after the same manner as ♄ and ♃ move about the Sun whilst the Satellites move about them especially since it is not demonstrated without much art and difficulty and taking many things for granted which are hard to be proved that there is any body in the Universe more considerable then the Earth we tread on Is there not much reason for the Hypothesis of Ticho at least when he with all the accurateness that he arrived to with his vast Instruments or Riccioli who pretends much to out-strip him were not able to find any sensible Parallax of the Earths Orb among the fixt Stars especially if the observations upon which they ground their assertions were made to the accurateness of some few Seconds What then though we have a Chimera or Idea of perfection and harmony in that Hypothesis we pitch upon may there not be a much greater harmony and proportion in the constitution it self which we know not though it be quite differing from what we fancy Probable Arguments might thus have been urged both on the one and the other side to the Worlds end but there never was nor could have been any determination of the Controversie without some positive observation for determining whether there were a Parallax or no of the Orb of the Earth This Ticho and Riccioli affirm in the Negative that there is none at all But I do affirm there is no one that can either prove that there is or that there is not any Parallax of that Orb amongst the fixt Stars from the Suppellex of observations yet made either by Ticho Riccioli or any other Writer that I have yet met with from the beginning of writing to this day For all Observators having hitherto made use of the naked eye for determining the exact place of the object and the eye being unable to distinguish any angle less then a minute and an observation requisite to determine this requiring a much greater exactness then to a minute it doth necessarily follow that this experimentum crucis was not in their power whatever either Ticho or Riccioli have said to the contrary and would thence overthrow the Copernican System and establish their own We are not therefore wholly to acquiess in their determination since if we examine more nicely into the observations made by them together with their Instruments and wayes of using them we shall find that their performances thereby were far otherwise then what they would seem to make us believe The Controversie therefore notwithstanding all that hath been said either by the one or by the other Party remains yet undetermined Whether the Earth move above the Sun or the Sun about the Earth and all the Arguments alledged either on this or that side are but probabilities at best and admit not of a necessary and positive conclusion Nor is there indeed any other means left for humane industry to determine it save this one which I have endeavoured to make and the unquestionable certainty thereof is a most undenyable Argument of the truth of the Copernican Systeme and the want thereof hath been the principal Argument that hath hitherto somewhat detained me from declaring absolutely for that Hypothesis for though it doth in every particular almost seem to solve the appearances more naturally and easily and to afford an exceeding harmonious constitution of the great bodies of the World compared one with another as to their magnitudes motions and distances yet this objection was alwayes very plausible to most men that it is affirmed by such as have written more particularly of this subject that there never was any sensible Parallax discovered by the best observations