# Philosophical Transactions of the Royal Society (1665-1886)/Volume 1/Number 2

Contents
* The Contents.
* Extract of a Letter, lately written from Rome, touching the late Comet, and a New one.
* Extract of a Letter, written from Paris, containing some Reflections on part of the precedent Roman Letter.
* An Observation imparted to the Noble Mr. Boyle, by Mr. David Thomas, touching some particulars further considerable in the Monster mentioned in the first Papers of these Philosophical Transactions.
* Extract of a Letter, lately written from Venice by the Learned Doctor Walter Pope, to the Reverend Dean of Rippon, Doctor John Wilkins, concerning the Mines of Mercury in Friuli; and a way of producing Wind by the fall of Water.
* An Extract of a Letter, containing some Observations, made in the ordering of Silk-worms, communicated by that known Vertuoso, Mr. Dudley Palmer, from the ingenuous Mr. Edward Digges.
* An account of Micrographia, or the Physiological Descriptions of Minute Bodies, made by Magnifying Glasses.
Numb. 2.
PHILOSOPHICAL
TRANSACTIONS.
Munday, April 3. 1665.
The Contents.
Extract of a Letter, lately written from Rome, touching the late Comet, and a New one.
Cannot enough wonder at the strange agreement of the thoughts of that acute French Gentleman, Monsieur Auzout, in the Hypothesis of the Comets motion, with mine; and particularly, at that of the Tables. I have with the same method, whereby I find the motion of this Comet, easily found the Principle of that Author's Ephemerides, which he then thought not fit to declare; and 'tis this, that this Comet moves about the Great Dog, in so great a Circle, that that portion, which is ​described, is exceeding small in respect of the whole circumference thereof, and hardly distinguishable by us from a streight line.
Concerning the New Comet you mention, I saw it on the 11. of February, about the 24. deg. of Aries, with a Northern latitude of 24. deg. 40. min. The cloudy weather hath not yet permitted me to see it in Andromeda, as others affirm to have done.
As to the Hypothesis of Georg. Domenico Cassini, touching the motion of the Comet about the Great Dog in a Circle, whose Centre is in a streight line drawn from the Earth through the said Star, I believe it will shortly be publish'd in print, as a thought I lighted upon in discoursing with one of my Friends, who did maintain, that it turned about a Centre, because that its Perigee had been over against the Great Dog, as I had noted in my Ephemerides. This particular I did long since declare to many of my acquaintance, whereof some or other will certainly do me that right, as to let the world know it by the Press. I have added an Observation, which I find not, that Signior Cassini hath made, viz. that there was ground to think, that the Comet of 1652. was the same with the present, seeing that besides the parity of the swiftness of its motion, the Perigee thereof was also over against the Great Dog, if the Observations extant thereof, deceive not. But, to make it out, what ground I had for these thoughts, I said, that if they were true, the Comet must needs acomplish its revolution from 12. to 12. years, or thereabout. But, seeing it appears not by History, that a Comet hath been seen at those determinate distances of time, nor that over against the Perigee of all the other Comets, whereof particular observations are recorded, are alwaies found Stars of the first Magnitude, or such others, as are very notable, besides other reasons, that might be alleged, I shall not pursue this speculation; but rather ​suggest what I have taken notice of in my reflexions upon former Comets, which is, that more of them enter into our Systeme by the sign of Libra and about Spica virginis, than by all the other parts of the Heavens. For, both the present Comet, and many others registred in History, have entred that way, and consequently passed out of it by the sign Aries, by which also many have entred.
I did found my Hypothesis upon three Observations only, viz. those of the 22, 26, and 31. of December. Nor have I done, as some have fancied of me, who having been able to observe the Comet, the 27, 28, 29, 30, and 31. of December, and to see the diminution of its motion, have judged, that I had only determined that diminution for the time to come, conform to the augmentation thereof in time passed until the 29. of December. For January 1. (on which day I composed my Ephemerides) I knew not (nor any person here) that the motion of the Comet did diminish; but on the contrary, most men believed, it was not the same Comet. But Signior Cassini knows very well, that that was not necessary, seeing that two portions of a Tangent being given, and the Angles answering thereunto, 'tis easie to find the position and magnitude of its circle. The reason, which I think the true one, of the diminution of its Motion in Longitude, and of its Retrogradation, by me conjectured in my Ephemerides, I began to be assured of, Febr. 10. For until the sixth, the Comet had alwaies advanced, as Signior Cassini also hath very well noted: but after that day, I found that it returned in augmenting alwaies its Latitude. And I have constantly observed it, until March 8. between many Stars, which must be the same with these mentione'd by Cassini, whereof the number was so great, that I think, I saw of them March 6. with one Aperture of my Glass, more than 40. or 50. and especially, above the head of Aries; but I did not particularly note the situation of more than 12. or 15; amongst which I have observed the position of the Comet since January 28. every day, when the weather did permit, viz. January 29. February 3, 6, 10, 17, 19, 24, 26, 27. and March 6, ​7, 8. I left it on March 8. at the 18. of the Horn of Aries, almost in the same latitude; and I am apt to believe, it will be Eclipsed; which I wish I may be able to observe this evening, if it be not already passed.
If Signior Cassini hath observed it on those daies that I have, he will be glad to find the conformity of our Observations. I shall only add, that on February 3. we were surprized, to see the Comet again much brighter than ordinary, and with a considerable Train. Some did believe, that it approach'd again to us. But having beheld it with a Telescope, I soon said, that it was joyned with two small Stars, whereof one was pretty bright, which I had already seen, on February 28. and 29: And this conjunction gave the Comet that brightness, as it happens to most of the Starrs of the fifth and sixth magnitude, where 2. or 3. or more are conjoyned, which perhaps would shew but faintly single, though by reason of their proximity to one another, they appear but one Starr. Hence it was, that I assured my friends here, that the following days we should no more see it so bright, because I knew, that there were none such small bright Stars in the way, which by my former observations I conjectured it was to move.
Upon the strictest inquiry, I find by one, that saw the Monstrous Calf and stone, within four hours after it was cut out of the Cows belly, that the Breast of the Calf was not stony (as I wrote) but that the skin of the Breast and between the Legs and of the Neck (which parts lay on the smaller end of the stone) was very much thicker, than on any other part, and that the Feet of the Calf were so parted as to be like the Claws of a Dog. The stone I have since seen; it is bigger at one end ​then the other; of no plain Superficies, but full of little cavities. The stone, when broken, is full of small peble stones of an Ovall figure: its colour is gray like free-stone, but intermixt with veins of yellow and black. A part of it I have begg'd of Dr. Haughten for you, which I have sent to Oxford, whither a more exact account will be conveyed by the same person.
The mines of Mercury in Friuli, a Territory belonging to the Venetians, are about a days Journey and a half distant from Goritia Northwards, at a place call'd Idria, situated in a Valley of the Julian Alps. They have been, as I am inform'd, these 160. years in the possession of the Emperor, and all the Inhabitants speak the Sclavonian Tongue. In going thither, we travell'd several hours in the best Wood I ever saw before or since, being very full of Firrs, Okes, and Beeches, of an extraordinary thickness, straitness, and height. The Town is built, as usually Towns in the Alps are, all of wood, the Church only excepted, and another House wherein the Overseer liveth. When I was there, in August last, the Valley, and the Mountains too, out of which the Mercury was dug, were of as pleasant a verdure, as if it had been in the midst of Spring, which they there attribute to the moistness of the Mercury; how truly, I dispute not. That Mine, which we went into, the best and greatest of them all, was dedicated to Saint Barbara, as the other Mines are to other Saints, the depth of it was 125. paces, every pace of that Country being, as they inform'd us, more than 5 of our Feet. There are two ways down to it; the shortest perpendicular way is that, whereby they bring up the Mineral in great Buckets, and ​by which oftentimes some of the workmen come up and down. The other, which is the usual way, is at the beginning not difficult, the descent not being much; the greatest trouble is, that in several places you cannot stand upright: but this holds not long, before you come to descend in earnest by perpendicular Ladders, where the weight of on's body is found very sensible. At the end of each Ladder, there are boards a cross, where we may breath a little. The Ladders, as was said, are perpendicular, but being imagined produced, do not make one Ladder, but several parallel ones. Being at the bottom, we saw no more than we saw before, only the place, whence the Mineral came. All the way down, and the bottom, where there are several lanes cut out in the Mountain, is lined and propt with great pieces of Firr-trees, as thick as they can be set. They dig the Mineral with Pick-axes, following the veins: 'tis for the most part hard as a stone, but more weighty; of a Liver-colour, or that of Crocus Metallorum. I hope shortly to shew you some of it. There is also some soft Earth, in which you plainly see the Mercury in little particles. Besides this, there are oftentimes found in the Mines round stones like Flints, of several bignesses, very like those Globes of Hair, which I have often seen in England, taken out of Oxes bellies. There are also several Marcasites and stones, which seem to have specks of Gold in them, but upon tryal they say, they find none in them. These round stones are some of them very ponderous, and well impregnated with Mercury; others light, having little or none in them. The manner of getting the Mercury is this: They take of the Earth, brought up in Buckets, and put it into a Sive, whose bottom is made of wires at so great a distance, that you may put your finger betwixt them: 'tis carried to a stream of running water, and wash'd as long as any thing will pass through the Sive. That Earth which passeth not, is laid aside upon another heap: that which passeth, reserved in the hole, G. in Fig. 1. and taken up again by the second Man, and so on, to about ten or twelve sives proportionably less. It often happens in the first hole, where the second Man takes up his ​Earth, that there is Mercury at the bottom; but towards the farther end, where the Intervals of the wires are less, 'tis found in very great proportion. The Earth laid aside is pounded, and the same operation repeated. The fine small Earth, that remains after this, and out of which they can wash no more Mercury, is put into Iron retorts and stopt, because it should not fall into the Receivers, to which they are luted. The fire forces the Mercury into the Receivers: the Officer unluted several of them to shew us; I observed in all of them, that he first poured out perfect Mercury, and after that came a black dust, which being wetted with water discover'd it self to be Mercury, as the other was. They take the Caput mortuum and pound it, and renew the operation as long as they can get any Mercury out of it.
This is the way of producing the Mercury, they call Ordinary, which exceeds that, which is got by washing, in a very great proportion, as you will perceive by the account annext. All the Mercury got without the use of Fire, whether by washing, or found in the Mines (for in the digging, some little particles get together, so that in some places you might take up two or three spoonfuls of pure Mercury) is call'd by them Virgin-Mercury, and esteem'd above the rest. I inquir'd of the Officer what vertue that had more, than the other; he told me that making an Amalgama of Gold and Virgin-Mercury, and putting it to the fire, that Mercury would carry away all the Gold with it, which common Mercury would not do.
The Engins, employed in these Mines, are admirable; the Wheels, the greatest that ever I saw in my life; one would think as great as the matter would bear: all moved by the dead force of the water, brought thither in no chargeable Aqueduct from a Mountain, 3 Miles distant: the water pumpt from the bottom of the Mine by 52 pumps, 26 on a side, is contrived to move other wheels, for several other purposes.
The Labourers work for a Julio a day, which is not above 6 or 7 pence, and indure not long; for, although none stay ​underground above 6 hours; all of them in time (some later, some sooner) become paralytick, and dye hectick.
We saw there a man, who had not been in the Mines for above half a year before, so full of Mercury, that putting a piece of Brass in his mouth, or rubbing it in his fingers, it immediately became white like Silver: I mean he did the same effect, as if he had rubb'd Mercury upon it, and so paralytick, that he could not with both his hands carry a Glass, half full of Wine, to his mouth without spilling it, though he loved it too well to throw it away.
I have been since informed, that here in Venice, those that work on the back-side of Looking-glasses, are also very subject to the Palsey. I did not observe, that they had black Teeth; it may be therefore, that we accuse Mercury injustly for spoiling the Teeth, when given in Venereal diseases. I confess, I did not think of it upon the place; but, black Teeth being so very rare in this Country, I think I could not but have markt it, had all theirs been so.
They use exceeding great quantity of Wood, in making and repairing the Engins, and in the Furnaces (whereof there are 16. each of them carrying 24. Retorts;) but principally in the Mines, which need continual reparation, the Fir-trees lasting but a small time under ground. They convey their Wood thus: About four miles from the Mines, on the sides of two mountains, they cut down the Trees, and draw them into the interjacent Valley, higher in the same Valley, so that the Trees, according to the descent of the water lye betwixt it and Idria: with vast charges and quantities of Wood they made a Lock or Dam, that suffers not any water to pass; they expect afterwards, till there be water enough to float these Trees to Idria; for, if there be not a spring, (as generally there is,) Rain, or the melting of the Snow, in a short time, afford so much water, as is ready to run over the Dam, and which (the Flood-gates being open'd) carries all the Trees impetuously to Idria, where the Bridge is built very strong, and at very oblique Angles to the stream, on purpose to stop them, and throw them on shore neer the Mines.
​Those Mines cost the Emperour heretofore 70000. or 80000. Florens yearly, and yielded less Mercury than at present, although it costs him but 28000. Florens now. You may see what his Imperial Majesty gets by the following account, of what Mercury the Mines of Idria have produced these last three years.
| 1661 | l. |
| Ordinary Mercury | 198481 |
| Virgin Mercury | 6194 |
| | 204675 |
| 1662 | l. |
| Ordinary Mercury | 225066 |
| Virgin Mercury | 9612 |
| | 234678 |
| 1663 | l. |
| Ordinary Mercury | 244119 |
| Virgin Mercury | 11862 |
| | 255981 |
There are alwaies at work 280 persons, according to the relation I received from a very civil person, who informed me also of all the other particulars above mentioned, whose name is Achatio Kappenjager; his Office, Contra-scrivano per sua Maestà Cesarea in Idria del Mercurio.
To give some light to this Narrative, take this Diagramme: F. is the water, C. B. a vessel, into which it runs. DG. EH. FI. are streams perpetually issuing from that vessel: D. E. F. three sives, the distance of whose wires at bottom lessen proportionably. G. the place, wherein the Earth, that pass'd through the sive D. is retained; from whence 'tis taken by the second man; and what passes through the sive E. is retained in H. and so of the rest. K. L. M. wast water, which is so much impregnated with Mercury, that it cureth Itches and sordid Ulcers. See Fig. 1.
I will trespass a little more upon you, in describing the contrivance of blowing the Fire in the Brassworks of Tivoli neer Rome (it being new to me) where the Water blows the Fire, not by moving the Bellows, (which is common) but by affording the Wind. See Fig. II. Where A. is the ​River, B. the Fall of it, C. the Tub into which it falls, LG. a Pipe, G. the orifice of the Pipe, or Nose of the Bellows, GK. the Hearth, E. a hole in the Pipe, F. a stopper to that hole, D. a place under ground, by which the water runs away. Stopping the hole E, there is a perpetual strong wind, issuing forth at G: and G. being stopt, the wind comes out so vehemently at E, that it will, I believe, make a Ball play, like that at Frescati.
I herewith offer to your Society a small parcel of my Virginian Silk. What I have observed in the ordering of Silk-worms, contrary to the received opinion, is:
1. That I have kept leaves 24. hours after they are gathered, and flung water upon them to keep them from withering; yet when (without wiping the leaves) I fed the worms, I observed, they did as well as those fresh gathered.
2. I never observed, that the smell of Tobacco, or smels that are rank, did any waies annoy the worm.
3. Our country of Virginia is very much subject to Thunders: and it hath thundered exceedingly when I have had worms of all sorts, some newly hatched; some half way in their feeding; others spinning their Silk; yet I found none of them concern'd in the Thunder, but kept to their business, as if there had been no such thing.
4. I have made many bottoms of the Brooms (wherein hundreds of worms spun) of Holly; and the prickles were so far from hurting them, that even from those prickles they first began to make their bottoms.
I did hope with this to have given you assurance, that by retarding the hatching of seed, two crops of silk or more ​might be made in a Summer: but my servants have been remiss in what was ordered, I must crave your patience till next year.
The Ingenious and knowing Author of this Treatise, Mr. Robert Hook, considering with himself, of what importance a faithful History of Nature is to the establishing of a solid Systeme of Natural Philosophy, and what advantage Experimental and Mechanical knowledge hath over the Philosophy of discourse and disputation, and making it, upon that account, his constant business to bring into that vast Treasury what portion he can, hath lately published a Specimen of his abilities in this kind of study, which certainly is very welcome to the Learned and Inquisitive world, both for the New discoveries in Nature, and the New Inventions of Art.
As to the former, the Attentive Reader of this Book will find, that there being hardly any thing so small, as by the help of Microscopes, to escape our enquiry, a new visible world is discovered by this means, and the Earth shews quite a new thing to us, so that in every little particle of its matter, we may now behold almost as great a variety of creatures, as we were able before to reckon up in the whole Universe it self. Here our Author maketh it not improbable, but that, by these helps the subtilty of the composition of Bodies, the structure of their parts, the various texture of their matter, the instruments and manner of their inward motions, and all the other appearances of things, may be more fully discovered; whence may emerge many admirable advantages towards the enlargement of the Active and Mechanick part of knowledge, because we may perhaps be enabled to discern the secret ​workings of Nature, almost in the same manner, as we do those that are the productions of Art, and are managed by Wheels, and Engines, and Springs, that were devised by Humane wit. To this end, he hath made a very curious Survey of all kinds of bodies, beginning with the Point of a Needle, and proceeding to the Microscopical view of the Edges of Rasors, Fine Lawn, Tabby, Watered Silks, Glass-canes, Glass-drops, Fiery Sparks, Fantastical Colours, Metalline Colours, the Figures of Sand, Gravel in Urine, Diamonds in Flints, Frozen Figures, the Kettering Stone, Charcoal, Wood and other Bodies petrified, the Pores of Cork, and of other substances, Vegetables growing on blighted Leaves, Blew mould and Mushromes, Sponges, and other Fibrous Bodies, Sea-weed, the Surfaces of some Leaves, the stinging points of a Nettle, Cowage, the Beard of a wild Oate, the seed of the Corn-violet, as also of Tyme, Poppy and Purslane. He continues to describe Hair, the scales of a Soal, the sting of a Bee, Feathers in general, and in particular those of Peacocks; the feet of Flies; and other Insects; the Wings and Head of a Fly; the Teeth of a Snail; the Eggs of Silk-worms; the Blue Fly; a water Insect; the Tufted Gnat; a White Moth; the Shepherds-spider; the Hunting Spider, the Ant; the wandring Mite; the Crab-like insect, the Book-worm, the Flea, the Louse, Mites, Vine mites. He concludeth with taking occasion to discourse of two or three very considerable subjects, viz. The inflexion of the Rays of Lights in the Air; the Fixt stars; the Moon.
In representing these particulars to the Readers view, the Author hath not only given proof of his singular skil in delineating all sorts of Bodies (he having drawn all the Schemes of these 60 Microscopical objects with his own hand) and of his extraordinary care of having them so curiously engraven by the Masters of that Art; but he hath also suggested in the several reflexions, made upon these Objects, such conjectures, as are likely to excite and quicken the Philosophical heads to very noble contemplations. Here are found inquiries concerning the Propagation of Light through differing ​mediums; concerning Gravity, concerning the Roundness of Fruits, stones, and divers artificial bodies; concerning Springiness and Tenacity; concerning the Original of Fountains; concerning the dissolution of Bodies into Liquors; concerning Filtration, and the ascent of Juices in Vegetables, and the use of their Pores. Here an attempt is made of solving the strange Phænomena of Glass-drops; experiments are alleged to prove the Expansion of Glass by heat, and the Contraction of heated-Glass upon cooling; Des Cartes his Hypothesis of Colours is examined: the cause of Colours, most likely to the Author, is explained: Reasons are produced, that Reflection is not necessary to produce colours, nor a double refraction: some considerable Hypotheses are offered, for the explication of Light by Motion; for the producing of all colours by Refraction; for reducing all sorts of colours to two only, Yellow and Blew; for making the Air, a dissolvent of all Combustible Bodies: and for the explicating of all the regular figures of Salt, where he alleges many notable instances of the Mathematicks of Nature, as having even in those things which we account vile, rude & course, shewed abundance of curiosity and excellent Geometry and Mechanism. And here he opens a large field for inquiries, and proposeth Models for prosecuting them, 1. By making a full collection of all the differing kinds of Geometricall figur'd bodies; 2. By getting with them an exact History of their places where they are generated or found: 3. By making store of Tryals in Dissolutions and Coagulations of several Crystallizing Salts: 4. By making trials on metalls, Minerals and Stones, by dissolving them in severall Menstruums, and Crystallizing them, to see what Figures will arise from those several compositums: 5. By compounding & coagulating several Salts together into the same mass, to observe the Figure of that product: 6. By inquiring the closenes or rarity of the texture of those bodies by examining their gravity, and their refraction, &c. 7. By examining what operations the fire hath upon several kinds of Salts, what changes it causes in their figures, Textures, or ​Vertues. 8. By examining their manner of dissolution, or acting upon those bodies dissoluble in them; and the Texture of those bodies before and after the process. 9. By considering, by what and how many means, such and such figures, actions and effects could be produced, and which of them might be the most likely, &c.
He goes on to offer his thoughts about the Pores of bodies, and a kind of Valves in wood; about spontaneous generation arising from the Putrefaction of bodies; about the nature of the Vegetation of mold, mushromes, moss, spunges; to the last of which he scarce finds any Body like it in texture. He adds, from the naturall contrivance, that is found in the leaf of a Nettle, how the stinging pain is created, and thence takes occasion to discourse of the poysoning of Darts. He subjoyns a curious description of the shape, Mechanism and use of the sting of a Bee; and shews the admirable Providence of Nature in the contrivance and fabrick of Feathers for Flying. He delivers those particulars about the Figure, parts and use of the head, feet, and wings of a Fly, that are not common. He observes the various wayes of the generations of Insects, and discourses handsomely of the means, by which they seem to act so prudently. He taketh notice of the Mechanical reason of the Spider's Fabrick, and maketh pretty Observations on the hunting Spider, and other Spiders and their Webs. And what he notes of a Flea, Louse, Mites, and Vinegar-worms, cannot but exceedingly please the curious Reader.
Having dispatched these Matters, the Author offers his Thoughts for the explicating of many Phænomena of the Air, from the Inflexion, or from a Multiplicate Refraction of the rays of Light within the Body of the Atmosphere, and not from a Refraction caused by any terminating superficies of the Air above, nor from any such exactly defin'd superficies within the body of the Atmosphere: which conclusion he grounds upon this, that a medium, whose parts are unequally dense, and mov'd by various motions and transpositions as to one another, will produce all these ​visible effects upon the rays of Light, without any other coefficient cause: and then, that there is in the Air or Atmosphere, such a variety in the constituent parts of it, both as to their density and rarity, and as to their divers mutations and positions one to another.
He concludeth with two Celestial Observations; whereof the one imports, what multitudes of Stars are discoverable by the Telescope, and the variety of their magnitudes: intimating with all, that the longer the Glasses are, and the bigger apertures they will indure, the more fit they are for these discoveries: the other affords a description of a Vale in the Moon, compared with that of Hevelius and Ricciolo; where the Reader will find several curious and pleasant Annotations, about the Pits of the Moon, and the Hills and Coverings of the same; as also about the variations in the Moon, and its gravitating principle, together with the use, that may be made of this Instance of a gravity in the Moon.
As to the Inventions of Art, described in this Book, the curious Reader will there find these following:
1. A Baroscope, or an Instrument to shew all the Minute Variations in the Pressure of the Air; by which he affirms, that he finds, that before and during the time of rainy weather, the Pressure of the Air is less; and in dry weather, but especially when an Easterly Wind (which having past over vast Tracts of Land, is heavy with earthy particles) blows, it is much more, though these changes be varied according to very odd Laws.
2. A Hygroscope, or an Instrument, whereby the Watery steams, volatile in the Air, are discerned, which the Nose it self is not able to find. Which is by him fully described in the Observation touching the Beard of a wild Oate, by the means whereof this Instrument is contrived.
3. An Instrument for graduating Thermometers, to make them Standards of Heat and Cold.
4. A New Engine for Grinding Optick Glasses, by means of which he hopes, that any Spherical Glasses, of what length ​soever, may be speedily made: which seems to him most easie, because, if it succeeds, with one and the same Tool may be ground an Object Glass of any length or breadth requisite, and that with very little or no trouble in fitting the Engin, and without much skill in the Grinder. He thinks it very exact, because to the very last stroke the Glass does regulate and rectifie the Tool to its exact Figure; and the longer or more the Tool and Glass are wrought together, the more exact will both of them be of the desired Figure. He affirms further, that the motions of the Glass and Tool do so cross each other, that there is not one point of eithers surface, but hath thousands of cross motions thwarting it, so that there can be no kind of Rings or Gutters made, either in the Tool or Glass.
5. A New Instrument, by which the Refraction of all kinds of Liquors may be exactly measured, thereby to give the Curious an opportunity of making Trials of that kind, to establish the Laws of Refraction, to wit, whether the Sines of the Angles of Refraction are respectively proportionable to the Sines of the Angles of Incidence: This Instrument being very proper to examine very accurately, and with little trouble, and in small quantities, the Refraction of any Liquor, not only for one inclination, but for all; whereby he is enabled to make accurate Tables. By the same also he affirms to have found it true, that what proportion the Sine of the Angle of the one inclination has to the Sine of its Angle of Refraction, correspondent to it, the same proportion have all the other Sines of Inclination to their respective Sines of Refractions.
Lastly, this Author despairs not that there may be found many Mechanical Inventions, to improve our Senses of Hearing, Smelling, Tasting, Touching, as well as we have improved that of Seeing by Optick Glasses.
London, Printed with Licence for John Martyn, and James Allestry, Printers to the Royal Society.