The Explication of the Figure aa The Beam. bb The Dishes cc The Frame to suspend the Beam upon which d a Sliding Socket e It's arm containing f a Pully over which g An other Poultry passes h A Line fastened to i A movable weight by which the Beam is raised up, & let down. k A Hair to suspend l The Body to be weighed in the water held in m The Glass Cestorn n The Buckit for Liquors o The Box of Grains p The Forceps to manage q The Pile of Weights r The handle of the Ballanc ssss The Table. Medicina Hydrostatica: OR, hydrostatics Applied to the MATERIA MEDICA. SHOWING, How by the Weight that divers Bodies, used in Physic, have in Water; one may discover Whether they be Genuine or Adulterate. To which is subjoined, A Previous Hydrostatical Way of Estimating OARS. By the Honourable ROBERT boil, Fellow of the Royal Society. LONDON, Printed for Samuel Smith at the Sign of the Prince's Arms, in St. Paul's Churchyard, 1690. THE PREFACE. I Am far from being fond of their Practice, that affect to give pompous and promising Titles to their Books; in so much that my Friends have several times reproached me with inclining too much to the opposite Extreme. But yet I am not averse from prefixing to the ensuing Paper, the Title of Medicina Hydrostatica; not only for the Conveniency of Citations, (which are usually troublesome to make in Tracts that have long Titles;) but because too I am Invited, if not Authorised to do it, by the Example of the famous and judicious Sanctorius; who scrupled not to prefix the Name of Medicina Statica, to a Writing almost as Small, as 'tis Ingenious, which applies the Balance to Some Uses relating to the Medicinal Art, perhaps not Moore, than will be here found proposed of the same Instrument, improved by some Additions. And 'tis scarce to be doubted, but that in this Inquisitive Age, the Sagacity of the Curious will make, both of what he has discovered, and of what I have delivered, useful Applications, that neither He, nor I, ever thought of. If the chief thing, I aimed at in Writing, had been to gain Applause, I would have taken a more likely way to obtain it, than by treating of a Subject, wherein few will think themselves concerned, (tho' many in reality be so, and whose Importance does not at first view appear.) And this Subject too, the Nature of it has obliged me, to treat of in such a way, that it will be almost as unpleasant to the Reader to peruse so unadorned a piece, as it was troublesome to the Author to writ so Toilsome an One. And indeed when I came to take notice of the Number of Particulars, that I had brought together into this little Book; I did myself somewhat wonder, how I came to be prevailed with to lay out so much Pains upon so uninviting a Subject. But Knowledge and Health are two such valuable things, that I durst not refuse to undergo, even a toilsome Task; whilst I was encouraged by the Hope, that was given me, that this kind of Labour may conduce somewhat to those desirable Ends; if not otherways, yet at lest by exciting the more curious among Physicians, Chemists, and Others, to enlarge their Inquiries, and by helping them to remark divers things relating to Medicinal Bodies, that they are want to overlook. I had probably better consulted my Reputation, as well as my Ease, if, having contented myself with those few uncommon Notions, and Observations, that the rest of the Book was built upon; I had left the Applications made of them to particular Bodies, to the industry of Others. I shall not solicitously excuse myself, for not having bestowed more Ornaments upon the following Essay; since the Nature of the Subject and Drift of the Writer, are sufficient to justify the Plainness of my Style to the Judicious. I may have somewhat more cause to Apologise for this; That I have not cast a Treatise about a Subject wherein Mechanics are so much employed, into the Form of Propositions; and given it a more Mathematical Dress. But I was unwilling by that means to discourage those many, who, when they meet with a Book, or Writing, wherein the Titles of Theorem, Problem, and other Terms of Art, are conspicuously placed, use to be frighted at them; and thinking them to be written only for Mathematical Readers, despair of understanding it, and therefore lay it aside, as not meant for the use of such, as they. But there is another thing, upon whose score, I confess, I aught to wish for indulgent Readers. For the Papers compiled into this Essay, having been written in lose Sheets, and at such distant times, that divers Accidents intervened between them; the loss of some of those Papers, as well as others of different Natures, and my want of Health, and Leisure, obliged me to change more than Once my proposed design, and to employ sometimes the Style of a private Letter, and sometimes again, that of a Discourse intended for the Public; By which, means some Things, and some Expressions, that were suitable to the Design I had, when I committed them to Paper, became incongruous, when the Scope and Scheme of my Discourse were altered, especially Some parts of the Copy being out of my hands, when I should have adjusted the Others to them. But tho' these Irregularities may keep the parts of this Essay, from being so coherent as they should be; yet they will not prove very prejudicial to an intelligent Reader; who, finding the Matters of Fact, and the Notions, to be true, may, notwithstanding the want of an uniform Contexture, make good use of them. Thou divers little Memoirs and other things, that occured to me from time to time, whilst I was bringing together the following Papers, have insensibly swollen them into a Book; yet the Essay itself was in my First intention, but a large Fragment of a greater work: whereof an Account is given in the Letter to a Friend, (that is premised to a Paper annexed to the following Essay,) which (Letter) having been intended for a kind of Preface to the last Scheme of the whole larger work; if the Reader please to peruse it, he will there found the Rise, and Scope of this little Tract, as well as of the other parts of that designed Book; and some other things, that may make it needless to lengthen this Preamble by any thing more than two Advertisements. Of these, One is, that, being reduced by divers unexpected, and unwelcome Accidents to forego my first design, and give only two or three Specimens of what was intended, and more than begun; I made choice of the Title of the Chemical Changes of Bodies by Coloration, as a Sample of the Chemical part of the Treatise; and I pitched upon the Subject of this present Essay, as a Specimen of the Mechanical part of the same Treatise; The other Advertisement, is, that the Reader need not be startled, to found some little Variations of Specific Gravity, among some of the Memoirs laid together in this Essay, because he will in due place be told, See the Chapters. why such things aught to be expected. And in the mean time, it may, I hope, suffice to say, that such Variations are neither new, nor easily avoidable things, in making Hydrostatical Experiments or others of Affinity to them. For Proof of which, to Readers, that, for want of having made Trials themselves, may distrust what we have said, I shall produce a Couple of notable Testimonies. The first is given by so industrious and diligent a Mathematician, as Mersennus himself. For he candidly acknowledges, when he has occasion to mention some Trials of the learned Ghetaldus, Varietas ponderandi, quae sepius in quibusdam Granis contingit, similis est Varietati Astronomicarum Observationum quae semper feré quibusdem minutis, sive Primis, sive Secundis differunt. Mersennus in Phoenominis Hydraulicis. and of the accurate French Engineer Monsieur Petit, & of his own; that the Variety of weighing, which often happens to amount to some Grains, is but like the Variety of Asstronomical Observations; which do almost always differ in some Minutes or some Seconds. To which he soon after adds an Intimation, that shows, that he expected not an exact uniformity between the Observations of Ghetaldus, etc. already made, and the Trials of an Experimenter, that would examine them by making the like again. To this first Testimony we shall subjoin the Second, which is, that our famous Experimenter, the Lord Verulam himself, writing of a Subject, that in several things has much Affinity with ours, confesses, that 'tis not to be doubted, but that many of the Bodies, which he has set down in his Table of their Dimensions, Hist. densit & Rarit. P. M. 12. Editionis Londinen. in Octavo. and Weights differ in the same Species or Denomination; some being heavier than others, and that therefore there is some Contingency in this Affair, so that 'tis not necessary, that the Individuals he made his Trials with should be exact Standards of the Nature of their respective Species, or should, (which makes directly to my present purpose) agreed altogether to a Title with Experiments of other Men. But this scarce evitable Imperfection of Hydrostatical and the like Experiments does not hinder, but that by their help we may make good Estimates of the Weights, and Bulks, of very many Bodies; and among them of not a few that belong to two sorts of the three, that our Illustrious Author acknowledges to be reducible to his Way of Mensuration. And these Estimates will (if I mistake not) be found, not only preferable to those that can be made of the same Bodies by Geometrical Instruments; but (which is more considerable for the Reader) accurate enough to be very useful on a great Number and Variety of Occasions. Which last Clause, I purposely add to insinuate, that the Hydrostatical Way of Mensuration may be usefully applied to several Bodies and Cases, that do not at all seem to relate to the Materia Medica, as would appear by inserting here what is delivered about Metrical, and about Exploratory Experiments and Observations, in other Papers; if that were not too foreign to the ensuing Essay, as not belonging to the Subject, or to the Design of it. Medicina Hydrostatica. The CONTENTS. Chap. I. THat Boles and lesle valued Stones may have as great Medical Virtues, as Gems. One quality only, viz. the Specific gravity of Fossiles, discovered by this way of exploring them. That Rock-Chrystal, being the most pure and Homogeneous kind of Stone, is pitched upon as the Standard, which in weight is, by computation, to clear Water of equal bulk, as two and an half to one. One Use of this way of weighing stony substances, viz. how far they partake of a Metalline Nature, or that of some other Mineral. From p. 1. to 7. Chap. II. The way of weighing sinking Bodies in Water. How to discover practically the proportion in weight, between the Solid and the Liquor. From p. 7. to 21. Chap. III. An account of several Solid Bodies thus examined, viz. Lapis Haematites, Lapis Lazuli, and Lapis Calaminaris. A Note, That the greater or lesser weight of such bodies, does not necessarily imply greater or lesser Medical Virtues, or Noxious Qualities in them. From p. 21. to 28. Chap. IU. A second use of this Hydrostatical way of Inquiry, viz. To found out, whether a Mineral Body propounded, as likely to be a stone, or of a stony Nature, be so indeed. This tried in Coral, Pearl, Calculus humanus and Bezoar. From p. 28 to 33. Chap. V A Third Use, viz. to discover, the resemblance, or the difference between bodies of the same denomination. From p. 33. to 35. Chap. VI A Fourth Use, viz. to discern genuine Stones, whether Animal or Mineral, from Counterfeit one's. From p. 35. to 39 Chap. VII. A Fifth Use, viz. to make probable Estimates of the genuineness, or the degree of purity of several bodies, that are, or may, usefully be employed in Physic, though they be not Stones or Minerals, provided they be heavy enough to sink in Water. An Advertisement to Jewellers, and Physicians, what Gems are to be most esteemed of by either. An experiment of fasing Zaphora with Venice Glass, as also a Granate. From p. 39 to 44. Chap. VIII. How to make Hydrostatical Inquiries into Liquids; for instance, Mercury. From p. 44. to 54. Chap. IX. The way of weighing Hydrostatically the Powders of sinking bodies, small sands, or the fragments of greater bodies. An Advertisement for the more exact weighing of these and other things. From p. 54. to 61. Chap. X. The way of Examining Hydrostatically a body that will dissolve in Water, or easily mingle with it, viz. to weigh it in Oleous Liquors (in Oil of Turpentine, for instance) which will not dissolve it. From p. 61. to 67. Chap. XI. How to found out by the hydrostatics, the gravity of fluid bodies, viz. by weighing some one solid body in as many of them, as you please. E. G. Amber in the lighter sort of Liquors; a Globular Glass Hermetically sealed with Quicksilver in it, or Rock-Chrystal, in either lighter or heavier. The Uses of examining Liquors by an Hydrostatical Solid. From p. 67. to 85. Chap. XII. Several ways to found out the weight of Liquids in Water, and other Liquors. From p. 85. to 93. Chap. XIII. Of what use this Hydrostatical Examination of Liquids' one in another, may be to Physicians. From p. 94. to 99 Chap. XIV. Two Reasons why, in many Cases 'tis not necessary the Scales employed in Hydrostatical Experiments should be extraordinary good. An Objection against this Method of finding out the weight of sinking bodies in Water, from the different weight of the Water that may be made use, answered. From p. 99 to 105. Chap. XV. Hydrostratical Stereometry applied to the Materia Medica. Sect. I How to found the weight of a Cubical Inch of Water; and how by means of this being found out, to found the dimensions of a Solid heavier in specie than Water. Sect. II. How to measure by the same means the solid Contents of a Body lighter in Specie than water, whether it be of that sort of Floating Bodies that are of a closer texture, than easily to be invaded by water; or of That, that so abounds with pores, as to be disposed to imbibe the water too much, while the Experiment is a making. The same Experiment's to be made in Oil of Turpentine, of Bodies that are apt to dissolve in water. From p. 105. to 130. Chap. XVI. Two Questions answered. The First, Whether I have proposed the best ways that can be thought of, to examine Bodies Hydrostatically? The Second, What credit may be given to the Estimates of the weight, and proportions of Bodies, obtained by Hydrostatical Trials? From p. 130. to 143. A Previous Hydrostatical Way of Estimating OARS. The CONTENTS. Sect. I. COntaining a fundamental Observation necessary, in order to make this previous Examen, viz. the finding out the Specific gravity of a pure Stone (v. g. Crystal, etc.) by the Hydrostatical way of Trial, delivered above in the Medicina Hydrostatica. From p. 151. to 154. Sect. II. A more general Use of the aforesaid Observation, viz. to found out, whether a Fossile have much, or little, or nothing, of a Metalline nature in it, by comparing its weight this way, with That of a pure Stone. Three Fossiles thus examined, viz. the Magnet, Emeri and Lapis Haematites. From p 154. to 159. Sect. III. and IV. Five Remarks to illustrate the former Observation, and make it more distinct. From p. 159. to 167. Sect. V A more particular notice taken of Marchasites, which by their shining streaks or other glistering parts, and their ponderousness, are apt to delude the Unskilful. From p. 167. to 172. Sect. VI An Advertisement to Examiner's of OARS, concerning Flux-powders. From p. 173. to 175. Sect. VII. and VIII. Some Observations about Native Gold, and the Hydrostatical Examen of Gold and its Ore. From p. 175. to 185. Sect. IX. The Hydrostatical way of exploring Sand-Gold. From p. 185. to 189. Sect. X. Two or Three Chemical ways of Examining Sand-Gold. From p. 189. to 194. Sect. XI. An Advice to those who are given to the search of Ours, to take notice of any Unknown or Vnommon Fossiles, they meet with; and to Examine them Hydrostatically. How to examine Oars, or Wombs, of Metals, which may be found disguised in the form of Earth or Mud, in an Hydrostatical Bucket. From p. 194. to 200. Sect. XII. That this last way of examen may be of use in divers Cases. p. 201.202 Sect. XIII. The most profitable use of the Hydrostatical Bucket, is, to use it in weighing variety of coloured Sands and Gravels. From p. 202. to 207. Sect. XIV. That there is such a thing as Volatile Gold; And that corpuseles of a Golden Nature may be in Fossiles, wherein they have not been suspected. From p. 207. to 209. Sect. XV. An advice to those who will apply the hydrostatics to Fossiles, that they procure Samples of Oars of the same Species out of different Ours; and found out what proportion of Metal they contain. From p. 209. to 215. An Advertisement concerning the Table annexed. p. 216.217. ERRATA. PAge 189. l. 3. r. Trial of such Wares. l. 4. deal, such Wares. p. 193. l. 3. r. or both. p. 195. l. 10. r. poise. p. 199. l. 4. deal, And. p. 205. l. 1. r. But therefore. p. 207. l. 3. r. the Operation. Medicina Hydrostatica: AN ESSAY. CHAP. I I have, in a former Tract, endeavoured (and, as I am told in Print, and otherwise, not altogether unsuccessfully) to make it probable, that divers, if not most, of the real Virtues (for many fabulous Ones have been ascribed to them) of Gems or precious Stones, may in great part proceed from the Qualities of Metalline and Mineral Substances, That, whilst the Matter was either fluid or soft, were (more or lesle plentifully) incorporated with the stony Matter, which hardened afterwards into a Gem. The same Phoenomena and Reflections, that led me to the Opinion newly recited, induced me to think it also very probable, that divers Bowls, Clayes, and other Earth's, and, much more, that several Minerals; which, tho' not looked upon as Metalline Oars, and several Stones or stony Substances, that, by reason of their Bigness or Opacity, or perhaps unpleasant Colours, have been judged unworthy to be numbered among Gems or precious Stones, may yet be endowed with considerable Medical Virtues; & perhaps with greater than the finer Gems themselves, because in these despised Stones and Minerals, there is often found a greater store of Metallic and Mineral parts, which while they were in solutis Principiis, as Chemists speak, might with ease plentifully insinuate themselves into these more open Bodies, where being settled they were not locked up so fast and strongly, as in the noble● Gems; such as Diamonds, Rubies▪ Saphires, etc. which are of so Compact, and as 'twere Glass-like, a Nature, that divers Corrosive Liquors, and Aqua Fortis itself, are unable to penetrate and dissolve them; tho', as hereafter will appear, these inferior Medical Stones, and other Minerals, may be opened by the like Menstruums. Upon these Grounds, I thought it might be a thing of use to Physicians, as well as to divers Mineralists and Mine-workers; if I imparted to them a Way of Exploring many Fossils', that I do not remember I had met with, either among Physicians or Chemists: And tho' this Way of Exploration pretends not to discover directly more than one Quality of the Body examined by it; yet that Quality, being its specific Gravity, is so radical and considerable a one, that it may lead a Sagacious Enquirer further than at first sight one would think. I considered than, that the most pure and homogeneous kind of Stones we know of, and that seems the freest from all adventitious Mixtures, and even * Tinctures TR's▪ is Rock-Chrystal: And therefore I pitched upon This, as the Standard I would employ, to make Estimates of the greater or lesser recess from Simplicity or Homogeneity of the Stones, or other Stone-like Substances, whose specific Gravity I should examine. We took than some Pieces of native Crystal, clear and colourless, and having carefully weighed them first in the Air, and than in Water, we found, by Computation, that pure Crystal was to clear Water of the same Bulk, as Two and an half, or thereabouts, are to One: So that, to clear the Matter by an Instance, if we suppose an hollow Cube, of Brass or other Metal, to be filled as carefully as may be, (for the upper Surface will scarce be exactly Levelly) with ℥ j of Water, and if afterwards the Cavity of the emptied Vessel be exactly filled with a Cubical piece of Rock Crystal; this Stone will weigh ℥ ij and about an half. Some of my Trials indeed, made with tender Balances, represented the Proportion of these two Bodies, with some petty Variation. But besides, that 'tis not improbable, that differing pieces of Rock Crystal itself, tho' of equal Bulk, may not be precisely equal in Ponderosity; besides this, I say, the Variation I found from the newly assigned Proportion was so small, that having just intimated, that for the most part it rather savoured a little the specific Gravity of the Crystal, than fell short of it; we may neglect it without any prejudice, worth taking notice of, to the Use that is to be made of this Proportion in this Paper. And for as much as there may be some Scruple, tho' groundless, made about the Origin and Nature of Crystal: I shall add, by way of Confirmation of what has been delivered, that I procured some strong Icicles, that had been fastened to Vaults, etc. as Bodies that would be acknowledged to be true Stones, and yet to have been in a Liquid Form; and having Hydrostatically examined these Concretions, the specific Gravity, tho' not exactly the same in all, appeared to be little differing from that of Crystal; the solid Body exceeding the Weight of the fluid water, it Was Weighed in, about two times and an half, (a little more or lesle.) Use I To apply this Fundamental Observation to the Uses designed in it, when I had a mind to make a probable Discovery, (for by this Way I pretend to no more) whether in a Stone, or Stone-like Body propounded, the merely stony Matter were more or lesle commixed with some adventitious Substance of a Metalline Nature, or that of some other Mineral more ponderous than Crystal, I carefully weighed it: First in the Air, and than in the Water, according to the Method formerly declared, and if by Virtue of its specific Gravity, its Proportion to Water of the same Bulk, exceeded the Proportion of five to two (which to avoid Fractions, may be commodiously substituted to that often already mentioned of 2 1/● to one) I concluded it probable, that the Concretion had in it a Portion of adventitious Matter, heavier in Specie than Crystal or mere Stone, by how much more or lesle the solid Body exceeded the Weight of Water equal to it in Bulk, by so much greater or lesser a Portion of Heterogeneous Matter was guest to be commixed with the stony in the propounded Concrete. This may be illustrated, as well as proved, by the Examples that should presently follow, but that it will be fit, before I descend to Particulars, to premise a Paper that concerns the whole Design of this Tract. CHAP. II. THO' the Way of weighing Solids in Water hath been delivered by the ingenious Marinus Ghetaldus, and, out of him, by some few other Authors, and tho' therefore I might excusably dispense myself from delivering it distinctly: Yet since their Books are scarce, and the knowledge of this Way is almost every where supposed in these Papers, I hold it very fit, that it should once be proposed in this Tract, not only for that Reason, but for Two others. One, that a dextrous way of finding out the Weight of Bodies in Liquors, may be of far more use than Men seem to be yet ware of, being capable of being made, by a little Variation and Improvement, of good use to Naturalists, and even to Chemists. And the Other, that perhaps you will found cause to think, that Experience and Reflections on it may have furnished me with some few Expedients and Cautions for the better Practice of this Art, and for the avoiding of some Errors, that may be very easily, and perhaps have been, run into, for want of the Cautions here given. The Way of weighing sinking Bodies in Water. The Solid Body, given to be examined, is to be tied about with an Horsehair of a competent length, which Hair at its other end is to be fastened to one of the Scales of a tender and exactly equilibrated Balance, so that, the proposed Body, being exactly weighed in the Air, and than immersed in a Glass or other fit Vessel, almost full of fair Water, may hung freely in that Liquor, being on every side encompassed by it. This done, you must put into the opposite Scale as many Weights▪ as serve to bring the Body hanging in the Water, to an exact Aequilibrium with the Counterpoise, and consequently the Beam of the Balance to an Horizontal Situation. Than take out the Weights newly employed, which give you the Weight of the Body in the Water, and deducting it from the Weight formerly taken of the same Body in the Air, and by the remainder, which will be the difference of these two, divide the whole Weight of the given Body in the Air, and the Quotient (whether consisting of whole Numbers, or a Fraction, or both) will show the Proportion, in specific Gravity, between the examined Solid, and as much Water as is just equal to it in Bulk. To make this more easily intelligible by an Example; We took a fine piece of white Marble, (that Stone seeming the most pure, and most free from Mineral Tinctures of any common opacous Stones) this being put into a good Balance, whose Scales were well equilibrated, was found to weigh in the Air, ℥ ij ʒiij ℈ 1. Grains IX. which, for Conveniency of Supputation, we reduce to 1169 Grains, than an Horsehair was tied about this piece of Marble, and the other end of the same Hair was fastened to one of the Scales, under which, at a convenient distance, was placed a somewhat deep Glass, almost full of fair Water, in this Liquor the Stone was made to hung freely, beneath the Surface, and in the opposite Scale, there were put Weights enough to bring it to an Aequilibrium with the other, these Weights were found, being reduced to the former Denomination, to amount to 738. Grains, which gave us the Weight of the Marble in Water, (which was much lesle Weight than the former, because the Stone was partly sustained by the Water) this being substracted from the Weight of the same Stone in the Air, there remained 431. Grains, which gave us the Weight of as much as was equal to the Stone in Bulk. By this remainder the Weight of the Marble in the Air, viz. 1169 being divided, the Quotient was found to be 2 & 71/100, or near enough 7/10 for the Proportion in specific Gravity of White Marble to water. The Demonstration of this Practice is founded on what I have elsewhere given, Hydrostatical Paradoxes. and it may, in another way, be found in some of the Commentators on Archimedes, de Insidentibus, humido. For understanding of the Summary Direction newly given, it may be useful to subjoin the following Notes: First, 'tis manifest by the Nature of the thing, that the Body, proposed to be weighed, aught to be heavy enough to sink in Water, since otherwise its Weight in that Liquor being none at all, cannot be significantly deducted from its Weight in the Air; but if there be occasion to Weigh in Water a Body lighter in Specie than it, as Bees-wax, a piece of Firr-wood, etc. It may be done, tho' not without some trouble, by joining to it a Body, heavy enough to make the Wax sink with it, but this Case belongs not to this place. 2. An Horsehair is made choice of, for Hydrostatical Operations, because it's said to be Equiponderant to so much Water; and tho' I have not found that to be strictly true, yet an Horse hair is fit to be employed in these Trials, than any other string, I know of; and its specific Weight usually differs so little from That of Water, that the Difference may be safely enough neglected; and if the Solid proposed be too heavy to be sustained by a single Horsehair, one may twist two, (or, if need be) more of them, to make the string strong enough to sustain the Solid. 3. I shall add, that I have met with Bodies, about which, by Reason of their Roundness, as in Bullets, or of some other inconvenient Figure, we could not well fasten an Hair, or other string, wherewith to tie it to the Balance. Now, on such occasions, I caused some Hairs to be so contexed, as to make a kind of a little Hoopnet, whose Meashes were not great enough to let the Body slip through them. In this small Vessel, whether you call it a Net or a Basket, which was tied by an Horsehair (single or twisted) to one of the Scales, we put the solid Body to be weighed, and proceeded in the Operation, as if the Body were tied but with a string. 4. But here it must be carefully noted once for all, that whensoever any Hydrostatical Trial is made with an Horsehair; there must be put into the Scale that holds the Counterpoise, as much of the same Hair, as can be guest to be of the same Weight with that part of the string that sustains the Body in the Water, which appears to be above the Surface of the Water; for this Liquor takes of the Weight only of as much of the Hair as is immersed in it, so that the unimmersed part of the string adds to the Weight of the Solid hanging in Water; and therefore, aught to be compensated by an equal Weight put into the opposite Scale. 5. When I kept a Balance, only or chief, for Hydrostatical Trials; I found it expedient, on divers occasions, to take of one of the Scales with the strings belonging to it, and substitute in its room a piece of Lead, or other Metal of a Conical, or some other convenient, shape, exactly Equiponderant to the opposite Scale, and at the same end of the string, to fasten one end of the Horsehair that tied the Body to be weighed in Water. And sometimes also, when I did not take of one of the Scales, I caused it to be perforated in the middle, (yet, without lessening its Weight) that so the Body, to be immersed, might hung very Perpendicularly from the midst of the Scale. The Motives, that induced me to these Practices, cannot be so well set down in few words; and therefore shall be now left unmentioned, especially because the Practices themselves, tho' on some occasions convenient, are not necessary. 6. There remain yet a couple of Remarks, which must lesle than any be pretermitted, if Men would avoid some Errors, that are but too often slipped into, by the Makers of Hydrostatical Trials. We are than (First,) to take notice, that the Body, to be examined, hung freely in the Water, so that no part of it any where touch the bottom or the sides of the Vessel, or reach above the upper Surface of the Water contained in it; for, if any of these Circumstances be not taken care of, (as it happens, when we are not heedful enough) the true Weight of the Solid is somewhat altered; and if any Corner, or other part of the Body, (and the like may be said of the Horsehair, 'tis tied with) tho' but a small one, appear above the Surface of the Water: That extant Portion, being not at all sustained by the Liquor, adds (more or lesle) to the Weight, that the immersed Body should have. Care also must be had, that, as nothing but the Water do touch the hanging Body, so, no part of the Water may touch the Scale whence it hangs. I have several times observed, that immersed Bodies have been concluded to weigh more in the Water than really they did; because, through such a want of Heedfulness, as is not uncommon, the Experimenters did not take notice, that if the string were too short, or the Vessel too full; the vibrating Motions of the Balance, would, at one time or other, carry down the Scale, the suspended Body was tied to, so low, as to make one part or other of it touch the Surface of the Water: some Drops of which Liquor would readily stick to it, and, because they adhered to the neither part of it, would lie concealed from an Eye that was not prying, and by consequence would sensibly add to the Weight of the Scale, and make the Body be thought heavier than indeed it was; which Oversight must needs be very prejudicial, when one makes Experiments that require Exactness. 7. But the most usual Cause of Mistakes i● Hydrostatical Trials, (especially such, as are made on small Bodies) wherein a little Error may be greatly considerable, is this; that Men are want to think it sufficient, (in these Trials) that the Body to be examined, be totally immersed in the Water; whereas it does not only often, but most commonly hap, that the given Solid, and the string that is tied about it, carry down with them divers Particles of Air; and perhaps too, it may found and extricate others, that lay concealed in the Pores of the Liquor itself; which Aerial Particles fasten themselves to the little Asperities, that they meet with on the Surface of the immersed Bodies, in the form of Bubbles, which, like so many little Bladders full of Air, endeavour to buoy up the Body they adhere to▪ and on that account do, in Proportion to their Number and Bigness, lessen the Weight, which the immersed body would otherwise have in Water. And therefore, great care is to be had, especially in nic● Experiments; that, by shaking the string, and warily knocking the Body against the sides of the Glass, the adhering Bubbles may be displaced, and emerge to the top of the Water▪ And I shall add a desire, that on some occasions this Caution be made use of more than once in the same Trials; because I have several times observed, that now & than after the immersed Body was freed from the first Bubbles that appeared about it, others did succeed, before an end was made of weighing the Body; out of some of whose unperceived Cavities, or Pores, (whether superficial or lying deeper) perhaps the latent Air could not easily on a sudden be driven by the Water. I have been the more Circumstantial in explaining the summarily proposed Method of Weighing Bodies in Water, because Experience hath shown, that 'tis not near so easy, as, upon the first reading of it, one would presume▪ to be exact in the Practice of it. Having obtained the Weight of a Body proposed; First, in the Air, and than in Water, according to the Method plainly delivered; 'twill not be difficult to discover Practically the Proportion in Weight, between the Solid and the Liquor. I say Practically, because the Rule is easy enough, tho' the Demonstration is not so readily to be understood by them, that are not acquainted with the Principles of the hydrostatics. The Theorem, upon which our Practice is grounded, was first, that we know of, delivered by the most sagacious Archimedes; whose Commentators have busied themselves in demonstrating it in a Mathematical way, as I have since endeavoured to do in a Physical way, and more easy to Naturalists in the Hydrostatical Paradoxes. Archimedes' Proposition is this, That a Body, heavier than Water, weighs lesle in Water than in the Air, by the Weight of as much Water as is equal to it in Bulk or Magnitude: Whence 'tis not difficult to deduce a Rule sufficing for our present purpose. For if you subtract the Weight of the Body proposed, whilst it is every way environed with Water; from the Weight of the same Body, which it was found to have in the Air; the residual Number or Difference gives you the Weight (taken in the Air) of as much Water as is equal in Magnitude to the Solid proposed; so that, having now two Bodies, one Firm, and the other Liquid, together with the Weight of each of them apart; to found their Proportion, you need but divide the greater by the lesser; and the Quotient compared to One, that is, to an Unite, will be the Antecedent the of the Proportion desired between the solid Body and the Water; which is mentioned, but, as it is the Liquor that is generally employed in these Experiments, for otherwise the Rule will hold, mutatis mutandis, in other Liquors, as well as in Water. CHAP. III. ANd now having premised these Remarks, and thereby made way for the clearer Understanding of the subsequent part of this Paper; we shall proceed to the Examples, that this not unnecessary Digression has diverted us from propounding. There is a deeply Read and Opacous Mineral, that commonly passes in the Shops under the Name of Lapis Haematites, tho' it seems to have more Affinity to that which divers Authors call Schystos. But whatever be the most proper Name that belongs to it, it is an hard Fossile, which, tho' little used by our English Physicians, is in several Places abroad in great Request; & that not without cause, as far as I can judge, by what I yet know of it; and especially, for that Somniferous Quality, that may be observed in some of its Preparations. But 'tis not here, tho' 'tis elsewhere, my Purpose to deliver its Medicinal Virtues; but only to examine, whether, according to our Method, it aught to be concluded to abound with Metallic Particles, (perhaps but Embryonated,) to whose Intermixture some of its Virtues may probably be ascribed. Therefore, in a very good Balance, having weighed a piece of English Haematites, that chanced to amount to about ℥ iij ʒijs ●/4, First, in the Air, and than in Water; we found its Proportion to this Liquor, as 4 15/100 to 1. At which Ponderosity, if I had not formerly made the like Experiments, I should have been surprised; as you probably will be, when you consider, that this Metalline Stone did not very much want of almost twice the Weight of a mere Stone of the same Bulk. This great Weight much confirmed me in the Conjecture I had made; that in this Lump was contained a good deal of Metalline Substance. And this induced me (to add that upon the by) to examine my Guests, by subliming it, when finely powdered, and diligently mixed with an equal, or double, Weight of Salarmonia●. For than having tasted, with the tip of my Tongue, of this Saffron-coloured Sublimate; I found it; as I expected, very Astringent or Styptic, as divers Preparations of Mars are want to be; and, for further Proof, having put lesle than a Grain of it into a spoonful or two of good Infusion of Galls; there was immediately produced a Black, and as it 'twere Inky, Mixture. Lapis Lazuli is sometimes made use of by European Physicians, but more frequently by Arabian and other Eastern Ones, for divers purposes, but especially to make Evacuations by Vomit. This Emetic Faculty seemed, likely enough, to belong to it upon the Score of a Metalline Ingredient; and accordingly, having examined Hydrostatically, a piece that was judged moderately rich, we found the Proportion of it to an equal Bulk of Water, to be as 3. to 1. which argues That, notwithstanding its briskness in Operation, it contained a much lesser Proportion of Metalline Substance, than Lapis Haematites, or divers lesle Operative Minerals. Observation about the Loadstone, as 'tis a Mineral. I elsewhere show, that the Loadstone may be applied to Medicinal Uses, and that it emits Effluvia, that are not Magnetical, and may have sensible Operations upon the Body of Man. On which account, it was not improper to examine it Hydrostatically; by which means I found, that the Weight of a Lump of Loadstone, that I judged to be either English or Norwegian; was in Proportion to Water of the same Magnitude, as 4 91/10● to 1. But of the specific Gravities of Lodestones, much more may be met with in another Paper. Lapis Calaminaris is often enough used in Physic, especially by Chemists, to dry; and to imbibe Acidities. For which Uses, I prefer it before divers more famous Drugs: But, tho' 'tis want to be employed, only as an external Remedy; yet some things, that I found in some uncommon Chemical Preparations of it, made me think, it may deserve to be further examined and tried. A famous and not unlearned Empiric, to whom I willingly communicated some Processes, that he desired of me; when I asked him about a Medicine, whose Success brought him a great number of Patients, for griping Fluxes, and some Dysenterical ones; candidly discovered his Medicine to me, and solemnly assured me, it was nothing, but pure and well-ground Lapis Calaminaris, seasonably given in a just Dose; as in a fit place I have more fully declared. This made it obvious for for me to conjecture, that Lapis Calaminaris participates of a Metallic Nature, as may be argued from its Operation upon Copper, which is thereby turned into Brass. Wherhfore weighing a piece of this Fossile, first in Air, and than in Water, it appeared to be to this Liquor as 4 169/100 to 1. If I had not among other Papers lost Some, wherein I had Registered a good Number of Trials of this kind made upon differing Fossiles; 'twould be easy for me to add to the four already recited, others manifestly conducing to the same Purpose. But presuming, that those already delivered may at present suffice; I shall now subjoin a few Observations, whereof the first may become the Candour and Impartiality of a Lover of Truth, and the rest intimate some further Uses of the Hydrostatical Way of exploring hard and ponderous Concretions, hitherto treated of. I must not therefore forbear to admonish you, that, tho' when an hard Fossile propounded, is found to be much heavier than Crystal of the same Bulk; 'tis a very probable Token, that in the Solid Concretion, there is a notable Portion, greater or lesser, of some Metalline or other ponderous Mineral Body, whence its good or evil Qualities, in reference to human Bodies, may probably be deduced; Yet, this hinders not, but that 'tis very possible, for a Fossile to be endowed with Medicinal Virtues, or to have noxious Qualities, on the account of a Portion of extraneous Matter; tho' its specific Gravity doth but little exceed that of Crystal, or the advantage seem but inconsiderable. For, (to pass by other Reflections) a very small Proportion of Adventitious, Metalline, or Mineral, Substance, if it be of an Operative Nature, may, in some Cases, suffice, to diffuse its self through the rest of the Mass, and impregnate it with active Qualities. Which may be partly Illustrated, and partly Proved, by some Experiments that will be hereafter met with, in one of the Chapters. CHAP. IU. Use II. TO hint somewhat about the further Utility of our Hydrostatical Way of Inquiry; I shall take notice in the first place, that it may assist us to guests, with probability, whether a Mineral Body propounded, as likely to be a Stone, or of a stony Nature, be so indeed. Thus Coral, for instance, is by some thought to be a Plant, by others a Lytho-dendron, but, by the greater Number, 'tis reckoned among Precious Stones. In this Dissent of Opinions, the specific Gravity may be of considerable Use. Wherhfore, we thought fit to weigh a piece of choice and well coloured read Coral; first, in the Air, and than in the Water, and found its Proportion to the Weight of as much of that Liquor, to be as 2 68/100 to 1. So that its specific Gravity much favours their Opinion, who take it to be a Stone, since it not only equals that of Crystal, but somewhat exceeds it. There are Some, that will have Pearls, because of their Hardness, and their being treated of by jewellers, and others that writ of Gems, to be of a stony Nature. Wherhfore I thought fit examine their Ponderosity also. But not having now with me any Trial of that kind; I shall substitute One that I made upon a monstrous Pearl, that was presented me by a Person that took it out of the Oyster. I call it Monstrous, because tho' it be well enough coloured, yet its Shape is irregular, and its Bigness extraordinary; as is also its Weight, amounting to full 206 Grains. This being weighed in Water, its Proportion in Gravity to an equal Bulk of the Liquor was found to be as 2 ●1/●00 to 1. So that its specific Weight was much about the same, with that of Crystal. There are Many, that take the Stones form in men's Bladders, for as true and genuine Stones, as Those that Nature forms in the greater World; and speak much, and sometimes not without ground, of the great Hardness of divers of them. But, tho' I deny not, that, in a laxer Sense, they may well enough pass for Stones; yet I should rather call them Animal Stones, than simply Stones; this Name having been constantly and generally used, to signify Mineral or Fossile Stones: which, by our Way of Exploration, may be easily distinguished from human Calculus', and other like hard Concretions, found in the Bodies of some Animals. For, having examined a good Number of these Stones, I found, that not only the Chemical analysis, I made of them, of which I elsewhere give an Account, manifested them, how hard soever they were, to be Concretions belonging to the Animal Kingdom, not the Mineral: But, by an Hydrostatical Examen of divers of them, I found them to differ much, in specific Gravity, from true Fossile Stones. Of this you will, in its proper place, meet with several Instances; so that it may here suffice to mention Two, that now chance to come to hand. Namely, that a Calculus humanus weighing above ʒujss was found to be in Proportion to an equal Bulk of Water, as 1 76/100 to 1. And another, that weighed ʒiv and above an half, in the Air, being also weighed in Water, appeared to be to this Liquor, as 1 69/100 to 1. I mention these Stones as belonging to the Materia Medica, tho' they are looked upon rather as Diseases, of which, indeed, they are very sad Productions, because a famous and experienced Physician, that Practised long in the East-indieses, and had better Opportunity than almost any European had before him, to try the Virtues of Bezoar, does either equal or prefer the Calculi, we are speaking of, even to Oriental Bezoar. And to show, that Men are not the only Animals, wherein Stone-like Concretions differ in specific Gravity, (and so may be distinguished, by that difference,) from Crystal and such like true Stones; we shall subjoin Two or Three Experiments, made upon choice Bezoar Stones, not exceeding a middle Size, such being the likeliest not to be adulterated. The first of these weighing in the Air ʒiij, and odd Grains, was found to be in Proportion to Water of the same Bulk, as 1 47/100 to 1. Another weighing somewhat lesle than ʒiij, was to the Weight of an equal Bulk of Water, as 1 53/100 to 1. I might add divers other Instances of the like Import; and though I think them not necessary, yet I shall subjoin One more, because 'tis afforded by a Bezoar stone, taken out of another of the same kind: This Kernel-stone, if I may so call it, being Weighed in the Air wanted Nine Grains of ʒiij, and its Proportion to Water of the same Magnitude, was found to be as that of 1 55/100 to 1. In all which Instances, we may observe, that these Animal Stones not amounting to twice the Weight of Water equal to them in Bulk, have lesle of specific Gravity, by above a Fifth part, than a true Fossile Stone (such as Crystal) is want to be endowed with. CHAP. V THE Use lately proposed of our Hydrostatical Way of Exploration, suggests to me Another, Use III. which may be deduced from it, as a kind of Corollary. This comprehends two, somewhat differing, Ways of applying the Observations, we have lately mentioned. For first, we may by the hydrostatics be assisted to discover, with Probability, the resemblance, or the difference that may be between Bodies of the same Denomination, so that some subordinate Species of them, may perhaps be distinguished, as well as several Individuals of the same, or lowermost, Species. Since, for Instance, we have found a notable difference between the specific Weights of several Lodestones, that were dug up in several Countries or Ours; if greater Number and Variety of Experiments, of this kind were made, we should possibly found, that, Caeteris paribus, the Lodestones of one Country, or of one Mine, are considerably heavier than Those of another; as, if I mistake not, I usually observed, the Norwegian and the English Lodestones to be heavier in Specie, than Those that are said to come out of a warmer Region, Italy; whose Island of Elba abounds with Ours, whereof I saw one entire Mass, that I judged to weigh a great many hundred of Pounds. And this difference of Weight between Fossiles of the same kind, when 'tis considerable, may be of good use to help us to distinguish between the Stones of the same lowest Species, that are proper to differing Countries or Ours▪ But, in Case the unequal Weight proceeds, as it often does, from an Adventitious Matter, that insinuated itself into the more genuine Matter of the Fossile, whilst 'twas Fluid or Soft, it may much assist us to guests at the greater or lesser Purity of Homogeneousness of the Fossile proposed; which Discovery may, on divers occasions, be of no small use to the Physician, the Jeweller, or the Naturalist. CHAP. VI BUT the Second thing comprised in our Corlolary, Use IU. may in divers Cases be of much greater Utility and Importance, as being very proper to help us to discern genuine Stones, whether Animal or Mineral, from sergeant Ones; which too often pass for true, to the great prejudice of Physicians and Patients, and the great Loss of Lapidarie's, and their Customers. For as there are few Qualities appertaining to ponderable Bodies here below, that are so radicated, (if I may so speak) as their Ponderosity is. So there is scarce any Quality, wherein 'tis so difficult for Impostors, to make a notable Alteration unperceivedly, as the specific Gravity. I said, for Impostors because, tho' in several Cases, 'tis not so very difficult, to altar the specific Weight belonging to this, or that, kind of Bodies; yet in those very Cases, it may be exceeding difficult, and perhaps impractible, to make a considerable Change in tha● Quality, but by such Additions, o● Operations, as will make a sensible Change in some other Qualities too and thereby expose the Fallacy to b● discovered. And this will especially prove difficult in many Cases to vulgar Cheats, and Counterfeiters, or Adulterators of Gems, and other valuable Minerals; because the little knowledge they have of the Numerousness, and Variety, of Natural and Artificial Productions, confines them to a small Number and Diversity of Means, to accomplish their fradulent Designs. And whilst they are intent, but upon counterfeiting the more obvious Qualities of things; and perhaps of eluding the known and vulgar Trials Men are want to acquiesce in; they are not like to take Care to maintain the specific Gravity, and secure their adulterated Wares, against an Hydrostatical Way of Examen, which, probably, they never so much as heard of. By this means, several Perls, for Instance, may be discovered to be Counterterfeit, without, in the lest, injuring them. And I remember, That some factitious Corals, that, for Divertisement, I made, to show what might be done in that kind; were, notwithstanding their fine Colour, Shape, and Glossiness, easily discoverable, by their having a specific Weight manifestly exceeding That, which belongs to natural Corals. Before I knew better Ways, I have sometimes, for Recreation, by the help of Minium made Pastes, or factitious Gems, which, tho' transparent, and finely enough coloured, yet, because they contained some vitrified Lead, added to the other Ingredients to promote the Fusion, were liable to be detected by an easy Hydrostatical Trial of their Ponderosity. I have likewise seen a fair Bezoar Stone, that so resembled a genuine Stone, That a great Price was set upon it. But being brought me to be judged of, I made little doubt of its being Counterfeit, by reason of its appearing to me as heavy as a Mineral Stone of that Bulk; tho' the Possessor being loath to expose it to an uncommon Trial, I could not so cogently evince, that I had a clear Reason to disadvise the purchase of it. CHAP. VII. AFter these Instances, (which are not the only, Use V. that might be alleged of this kind) the affinity of the Subjects invites me to take notice of another Use, or, at lest, a Variation of the former, which may be made of our Hydrostatical Way of examining Solids. For it may, on divers occasions, assist us, to make probable Estimates of the Genuineness, or the degree of Purity of several Bodies, that are, or may, usefully be employed in Physic; tho' they be not Stones or Minerals, provided they be heavy enough to sink in Water. For when we have once found the specific Gravity of a Concretion of this sort, that we know to be Genuine, and well-conditioned in its kind; this degree of Ponderousness may serve us for a kind of Standard, whereby to judge of others, of the same Denomination, or that are said to be of a like Nature. To illustrate a Remark, that has no more of Difficulty in it than This, fewer Instances will suffice, (if any be necessary) than you will meet with in the following Part of this Tract, wherein they will opportunely occur. And therefore, instead of setting them down in this place, I choose to give you an Advertisement, that would surprise you, if I had not formerly hinted somewhat, appliable to the same purpose, by no great Variation. For that which I am about to observe to you, is, That, I think, there should be made a great difference between the Estimate, that Men make of some Stones, to which the Shops give the Name of Gems, according as the Estimate is to be made by Jewellers and Goldsmiths, or by Physicians and Chemists. For the Tradesmen, who usually aim but at the Beauty and Lustre of the Gems they would Cell, may justly esteem those Caeteris paribus the best, that are in Specie the lightest, because such are generally more uniform as to Sense, and more Transparent; and also, receive their Colour from Pigments of finer Parts. But, on the contrary, those, that in Gems seek mainly, if not only, for the Medicinal Virtues; may justly value Those most, that are most Ponderous: as having more plentiful Portions of the Metallic, or Mineral, Substances, whence the greatest part of their Virtues is, as has been formerly noted, in Probability, to be derived. And this difference in specific Weight, in Stones that have the same Name given them, I sometimes found to be far greater, than one that has not tried it would imagine, as may appear by some Instances, applicable to this Argument, that will hereafter be met with. But yet, I would not hence infer, that even such Stones, whether transparent or not, as appear fine, and are but light in their kind, must be devoid of Particles, whether Metalline, or of kin to them, whence they may be endowed with considerable Medicinal Virtues. For there are Mineral Pigments of so subtle a Nature, that so small a Quantity as will scarce make them sensibly heavier than Gems that are lesle, or perhaps not at all coloured, may be diffused through the whole Matter; and, at lest, impregnate every sensible part of it: This I shall Illustrate by the following Experiment, devised for that purpose. Five Grains of powdered Zaphora, being mixed with ℥ i ʒ ss of finely powdered Venice Glass, and kept a full hour in Fusion in a Furnace, that gives an exceeding violent Fire, afforded a transparent Mass, that was throughout of a fine blue Colour, and that deep enough; so that one part of the Pigment sufficed to tinge, by Fusion, above an hundred parts of the Glass: And when for Curiosity, we made the Proportion of the Zaphora a little greater, taking Eight Grains of the Pigment to ℥ i of Glass, that is, One to sixty; the Mixture having been kept for the like time in strong Fusion, the Mass was so deeply coloured, that the Proportion of the ting stuff to the rest of the Water, appeared too great to make a handsome Gem. And further to manifest, that a Quantity of Metalline Matter, tho' it be but very small, may suffice to give a Tincture, and so to impart a Virtue to a Glassy Body, and even to Gems; I shall add an Experiment, that perhaps you will think somewhat strange. I had long conjectured, that there was in Granats, especially in some that were deeply coloured, pretty store of Metalline Corpuscles of a Martial Nature, and that those Corpuscles are more than sufficient for the Granate itself, into whose Composition they enter, tho' not visibly, because of their extreme Minuteness. Upon this supposition, I took a Bohemian, or rather German, Granate, (for I never saw any Bohemian so large) that I had kept by me for a Rarity, because of its Bigness and deep Colour, though it was not a fine Stone to look on, notwithstanding its being transparent in those Edges that were thin. This being reduced to very fine Powder (but not in an Iron Mortar, jest should take something from the Metal) we exactly mixed Eight Grains with an Ounce of finely pulverised Crystalline Glass; afterwards the Mixture was kept two hours in a Furnace, that gives a stronger Fire than ordinary Wind-furnaces, by which means we obtained, as I expected, a pretty uniform Mass tinged of a sufficiently green Colour, such as prepared Iron, or Steel, gives to pure Glass. CHAP. VIII. WHat has been hitherto delivered, may serve to show, in some measure, the Uses of our Hydrostatical Way of examining Drugs, upon a Supposition that they are Solid, and neither very minute, nor too light to sink in Water. But I must not forbear to confess, and even give Notice, that there are many Simples, and other ponderable Substances, that may, upon good Grounds, be said to belong to the Materia Medica; which yet want One, or Moore, of the newly expressed Conditions. Wherhfore I must not conceal, that there are Three things, which, tho' not necessary to the Understanding of the Usefulness of the foregoing Part of this Discourse; may, if they can be performed, much conduce to Facilitate (for I dare not say, to Complete) the Hydrostatical Way of examining Bodies, heavier in Specie than Water. And therefore, tho' I confess it no easy Task to surmount the Difficulties to be met with in this Attempt; yet I shall endeavour to lessen them as much as I can, by offering to you the Expedients, that I was want formerly to make use of in the Three Cases, I am about to mention: Namely, First, When the Body to be examined was Liquid, and consequently, I could not be immediately taken hold of by an Horsehair, or any other slender String. Secondly, When the Body proposed was either in the Form of Powder, or consisted of Fragments that were so small, that it 'twas not possible, or, at lest, not fit, to fasten each of them to an Hair; and suspend it after the manner of a Body of a greater Bulk. And, Thirdly, When the Solid to be Hydrostatically examined, though great enough in Bulk to be tied about, was dissoluble in Water; and consequently unfit to be weighed in that Medium: Since therein its Gravity must continually decrease, whilst the Operation was performing. As to the First of the Three Difficulties; lately mentioned, I suppose, I need not solicitously premise, that the Liquid Substance, to be Hydrostatically examined, aught to be heavier in Specie, than the Water, or other Fluid, 'tis to be weighed in; and of such a Nature, as not to be apt (at lest, speedily) to mingle itself with it: since, otherwise, the proposed Liquor will either emerge in that it should be weighed in, or else be confounded with it, and so retain no distinct Mass, or Gravity. Supposing than, that the Liquor, to be examined, has belonging to it the Two newly recited Conditions, we made use of this Expedient to explore its specific Weight. We took a small Jar, or wide-mouthed Glass capable of containing an Ounce or two of common Water, and weighing in the Air about, Three or four Drams (more or lesle, as occasion requires.) This Glass, which▪ for Brevity's sake, we are want to call Hydrostatical, or else Glass-Bucket; we weigh very carefully once for all, first in the Air, and than in the Water, and by the difference of the Weights we found, according to the known Hydrostatical Method, a Weight equivalent to That of the Substance of the Glass in Water is so that such a Weight being put into the opposite Scale of the Balance, the Vessel hanging under the Surface of the Water, may be considered as having no Weight at all, that is, no Praeponderancy. And consequently, the Weight of a Body contained in this Bucket may be looked upon, as That of the Body itself in Water, without being increased by that of the Vessel; so that, in our Instance, the Bucket makes a Mass of Quicksilver, tho' Fluid, as ponderable as if 'twere coagulated into a Solid Body. The Glass-Bucket being thus provided once for all, we put the proposed Mercury into it, and weigh them together in the Air; whence deducting the already known Weight of the Vessel itself in the Air, the Residue gives the Weight of the Quicksilver alone in the Air. This done, by the help of an Horsehair, we tie the Bucket to one of the Scales, (or to either end of the Beam,) and letting it, with the Quicksilver in it, slowly sink into a Glass, or other Vessel, competently full of fair Water, and hung so, that the Bucket may not any where touch, either the bottom, or the sides of the larger Vessel; we reduce by Weights, put into the opposite Scale, and added to the formerly mentioned Counterpoise of the Bucket in the Water, the Balance to an exact Aequilibrium, without raising the Bucket quite to the Surface of the Water; this newly obtained Weight, of the immersed Quicksilver, being deducted from its Weight in the Air, 'tis easy, by the known Hydrostatical Method, to obtain the Proportion in Gravity, between the given Mercury, and an equal Bulk of Water. To expedite this Operation, it may be convenient to have in readiness (as I was want to do,) a couple of Weights, of Lead, or Tin; the greater exactly equal to the Weight of the Glass-Bucket in the Air, and the other equal to the Weight of the same Bucket in Water. For, by keeping these two Weights constantly in readiness, One has at hand a Counterpoise of the Vessel, in which soever of the two Medium's 'tis employed in; which saves them, that have frequent occasion to use the Balance, much of the time that must otherwise be spent to adjust it. This Advertisement being premised, the lately propounded Operation will be best understood by an Example; we took a small Glass-Jar capable of holding about ℥ ss. of Water, and put it into one Scale of a tender Balance; whose other Scale we furnished with a Counterpoise, or Weight, equal to the Glass. Into this little Vessel, we than put ℥ 1, that is, Four hundred and eighty Grains of Mercury (affirmed to be Spanish, which is counted the richest) and the Glass with this Mercury in it was, by an Horsehair, made to hung from one of the Scales, into a deep Glass Vessel of Water. Whilst it wa● in that state, there was in the opposite Scale a Counterpoise to the Glass itself in the Water, so tha● the Drams and Grains, that 'twas requisite to add, gave us the Weigh● of the Quicksilver only, the Weigh● of the Glass, being already accounted for. But Care was first taken, that the open-mouthed Vessel should be every where environed with Water, and diligently freed from adherent Bubbles; and that a piece of Horsehair should be added to the Counterpoise, to compensate that part of the String or Hair tied about the Bucket, that was in the Air, intercepted between the Scale, it was fastened to, and the Surface of the Water. By this means, we found the Weight of the Quicksilver in that Liquor, to amount to 446 Grains, which being substracted from the Weight of the Quicksilver in the Air, the difference was 34 Grains, by which the greater Number being divided, the Quotient was 14 and about 1/1●. So that the Mercury, employed in this Operation, appeared to be in Gravity to Water of the same Bulk, as 14 11/●●● to 1. I said, the Mercury employed in this Operation, because, in former Trials, I scarce found common Quicksilver, that was bought in Shops, to weigh full Fourteen times, and sometimes scarce 13 and ½ as much as a Bulk of Water equal to it; whether the Ponderousness of our last used Mercury proceeded from hence; that, as some Chemists extol Spanish Mercury, as participating more than others of a Golden Nature, (which Opinion, a Trial, that I purposely made of That employed about the late Experiment, did not disfavour;) So, there was in this of Ours something of unfixt Gold, that somewhat increased its Weight; I leave to further Enquiry. If you can command, as I cannot, the Learned Ghetaldus' Archimedes Promo●us: Since, as I am informed, He there sets down the intensive Weight of Quicksilver Hydrostatically found; it may be worth your while to consult that scarce Book, and compare the things you may meet with there, relating to Quicksilver, with what I have now delivered. To which I shall add, That this I may here give you Notice of in general; That, having on Chemical and other Accounts, had more occasion than most Men, to make Trials of this sort, I did not found all running Mercuries, tho' they did not appear adulterated, to be precisely of the same Weight: Nay, even destilled Mercuries, if once combined with Metalline Bodies, and particularly, if they were animated, and drawn from fine Gold; I found to differ more from common Mercuries sold in Shops, than These did from one another; and even between common Mercuries, notwithstanding their having been Destilled, we found a notable Disparity. But to enlarge on this Subject, were improper in this Place, where I mentioned the Weight of Mercury: But to give so clear (tho' but single) an Instance of the Way of measuring the Weight of ponderous Liquid Bodies in Water, as may warrant me to say; That, by this Method, tho' not always with the same ease, we may explore the specific Weight of other Liquors, that are in equal Bulk heavier than Water, and yet are indisposed to mingle with it; such as are the Chemical Oils of Cinnamon, Cloves, Guajacum, etc. But the chief thing, that has made me the the more Circumstantial in delivering the foregoing Experiment, was, that this practical Direction, for weighing one Liquor in another, will hereafter appear to be appliable to useful Purposes, especially when we come to mention, in the following Chapters, several Cases, wherein Liquors of a Nature very different from Water, may be substituted in its stead. CHAP. IX. AS for the Way of Examining Hydrostatically the Powders of sinking Bodies, such as Minium, Puttie, etc. or such small Solids, or Fragments of greater Ones, as by reason of their Littleness or inconvenient Shape, are singly unfit to be tied with an Horsehair to the Balance; as the Fragments of Rubies, and other precious Stones, want to be sold by Weight at the Drugster's or Apothecary's Shops: the Way of discovering the Weight of these in Water, differs not much from That lately delivered of weighing Quicksilver in that Liquor. For on these occasions also, we employ such a Glass-Bucket, as was lately described; and having made it very dry, as well within, as without; We put into it the Metalline Calx, or other heavy Powder, or a convenient Quantity of the Fragments of Gems, or a competent Number of small, tho' entire, Bodies, as Pieces of Native Cinnabar, Seed-pearl, etc. and proceed with these, as we did with Quicksilver. Only this Caution is to be heedfully taken along, that we warily, and little by little, put into the Bucket, whilst 'tis yet kept in the Air, and hath the already weighed Powder, or Fragments in it, a convenient Quantity of the same Water, 'tis to be weighed in; that the Liquor may have time to insinuate itself between the dry Bodies, and even the Corpuscles of the Powders, and expel thence the Air, that was harboured in the Intervals betwixt them; which little Aerial Portions, if not thus seasonably expelled, would, upon the immersion of the Vessel, produce in the Water store of Bubbles, that would buoy up, or fasten themselves to the Fragments, or other small Bodies, and make the Experiment uncertain, or fallacious. And if it be a Powder, that is to be weighed; unless it be before hand throughly wetted, and thereby freed from Aerial Particles, and reduced to a kind of Mud; there is Danger, that some dry Corpuscles of the Powder, will, when the Vessel is under Water, be buoyed up, and get out of it, and, floating on the Surface of the incumbent Water, take of from the true Weight, that the immersed Powder should have in that Liquor. If this Way of examining Bodies be carefully employed by a dextrous Man, furnished with a tender Balance, it may be of considerable use, not only to Physicians, Druggist's, and Apothecaries, that are conversant with the more precious Kind's of sinking Bodies, that belong to the Materia Medica; but also to Lapidaries, and Goldsmiths, whom it much concerns not to be imposed upon by sergeant Gems, or by other Stones of price, that are not duly conditioned, in their kind. Thus the Fragments of the Five precious Stones, That (upon what grounds, I now inquire not,) are made Ingredients of some Noble Compositions, as Confectio Hyacinthi, etc. these Fragments, I say, may each sort of them apart be usefully examined by their Weight in Water, by him that knows the true specific Gravity of a parcel of the finest, or else of such as he judges to be fittest for his purpose. And, to add That upon the By, whereas Granates are reckoned among the Five Medicinal precious Stones, and in some Pharmacopoea's are preferred to the First place, as the best: I have found so great a difference, in point of Ponderosity, between European Granates and American Ones, whereof some were sent me as a Present from New England, and others, I myself picked plentifully enough out of an odd American Mineral, that I suspected to contain them; that it was very obvious to think, their Virtues might be very different, if not as to Kind, yet, at lest, as to Degrees: And not only such factitious Pearls as have deluded many, and sometimes even famous, Jewellers, (as one of themselves, that was Lapidary to a great Monarch, confessed to me) may oftentimes by this Expedient be discovered, especially if Mercury (tho' disguised) be employed in making them; but, we may probably by the same Method discriminate the natural Pearls of several Countries and Sorts, whereof I have seen a far greater difference than one would expect; and I have somewhere yet by me natural Pearls of such various Colours, as well as Shapes, as have somewhat surprised even the Curious. But because it more concerns Physicians and Patients, to be able to make Estimates of Seed Pearl, that are on many occasions of good use to health; than to know the Genuineness of those bigger Ones, that are seldom made use of, but for Ornament; I shall here mention the result of an Experiment, which I found among my old Notes, to have been made by me, when I was furnished with very fine Oriental Seed-Pearls. For having examined these by the Way, we are now discoursing of, as judging them Orient enough to be fit to be Patterns, wherewith to compare Others; we found these to Water of the same Bulk, 2 75/100 (i e. ¾) to 1. But in This, and in those other Trials, whose Difficulty, or Importance, require, that we make them as exactly, as we are able. I must advertise you, that 'tis not fit to trust to the Steddiness of your hand, in holding the Balance, but that you make use of a Gibbet, (as they call it,) or some other stable Prop to support it. For the Hand often shakes, and makes the Instrument that it holds, to do so: and oftener grows weary before the Scales have had time to play up and down, and at length settle in a determinate Situation; wherein if you miss of a true Aequilibrium, the Hand must undergo a new Penance: Whereas, when the Balance hangs on a stable Fulcrum, you have both your Hands to help you, and need not be tempted by Weariness to desist, before the Balance be brought to rest in a perfect Aequilibrium. The Neglect or Omission of this Practice, I take to be one main Reason, (for the want of good Balances, or of Skill to use them, is oftentimes Another) why so many of the Experiments, that require weighing, are Erroneous; as they that cautiously examine them (as I have sometimes had occasion to do) may easily found. And therefore, (to add That, upon the By,) I hope, you will not make haste to censure the Accounts I give of Hydrostatical Trials, because they do not always agreed with Those of other men's; since perhaps they did not employ, either more Diligence, or better Instruments, than I CHAP. X. THe last of the Three Cases, formerly mentioned: Namely, What is to be done, when the Body to be Hydrostatically examined, will dissolve in Water, or easily mingle with it? Imports a Question, difficult and troublesome enough to be resolved. Nor can this Examen be performed by a single Operation, which yet sufficed in each of the Two foregoing Cases. And having seriously considered the Matter, the best Expedient I could than think of was, That, which divers years ago, I propounded in an Assembly of the Royal Society, and grounded on this Reflection, That tho' the Body proposed could not be immediately weighed in Water, yet we may substitute another Liquor that will not dissolve it, and thereby investigate the specific Gravity, in reference to that Medium; and than, by comparing the difference of those Two Liquors in point of Gravity, One may come to discover, What the Body proposed would have weighed in Water, in case it could have been kept there a competent time, without having any part of it dissolved. Considering than, that, except Quicksilver, the visible Fluids we can command, are either of an Aqueous, or of an Oily, Nature; and that most Bodies, whereof we can make Solutions in Liquors of the former, will not (at lest, sensibly) suffer themselves to be dissolved by those of the later, Kind, whilst a proposed Solid is weighing in them: We presumed that the most Saline Bodies, such as Alum, Vitriol, Sal Gem, to which may be added, Borax, Sublimate, etc. might be commodiously weighed in Oleous Liquors. Among these I made choice of Oil of Turpentine, rather than Oil- Olive, or any Chemical Essential Oil: Partly, because, being of common use, 'tis to be procured in sufficient Quantity, and, being very cheap, is seldom adulterated, as Chemical Oils are too often found to be; and, partly, because being a distilled Body, it may be presumed to be free from Aqueous Parts, of which Experience has shown me, that common expressed Oil is far from being destitute: But because Two Liquors, that are indeed both of them Oils, are want to have distinct Names given them in the Shops; I shall here intimate, that I do not, when I have my Choice, make use of that which many call the Oil of Turpentine, but of That which first comes over, which those that distinguish them, call the Spirit of Turpentine: I prefer This, (I say,) because 'tis clear, almost like fair Water; whereas, That which is called the Oil, besides that 'tis lesle Fluid, is commonly of a Yellow Colour, which does lessen its Transparency, and may be compounded with some of the coloured Bodies to be weighed in it. There are many Persons, that would found it very difficult, and to whom, on most occasions, 'twill not be necessary, to know the determinate Proportion in Gravity, between Oil of Turpentine, and the Solid that is weighed in it; and to discover, by the help of that Gravity, what the Body proposed would weigh in Water, in case it could be kept for a competent time in that Medium, without having any part of it dissolved therein. And therefore, Thou, if you desire it, I shall, God permitting, annex the Method of performing this Task (which, you know, requires more Calculation, than every common Reader is able to go thorough with) to the end of this Tract: Yet, for the present it may perhaps be sufficient, as well as fit, that I give you notice, that those, that have not Skill enough to determine, by the hydrostatics, the Proportion between sinking Solids, and the Liquor they are weighed in, may yet be assisted by what we have delivered about Oil of Turpentine, to make a not unuseful Estimate, What is the specific Gravity of divers Bodies, in reference to others of the same, or a differing, Species; and by that means, to make a probable Guests, Whether or not it be rightly Conditioned; if he be but provided with one piece of the Body, which he knows to be Genuine or well qualified. For This may serve him as a Standard, whereby to examine other Bodies of the same Denomination, that he may have occasion to Purchase, or to Cell, or to Employ. As, suppose a Tradesman be to buy a parcel of Sublimate, he may take an Ounce, for instance, or half an Ounce of some of That he knows to be good or rightly made: Than having carefully weighed it in Oil of Turpentine, and set down how much it weighs therein; if he takes an Ounce, or half an Ounce of the Sublimate, he would make Trial of, he may weigh that, as he did the other, in the same Liquor, wherein if it give the same Weight with the Standard, 'tis a good Sign; but if it weighs not so much, 'tis a Sign that it has not its full or due Proportion of Mercury, and too great a Proportion of Salts, whence its comparative Lightness proceeds. The same Way of trying may be made use of, for the Examen of Mercurius Dulcis, and divers other Bodies, totally or partly, dissoluble in Water, as of Alum, which is often Sophisticated with some base Salt; and of Roman Vitriol, which is sometimes either counterfeited, or adulterated by the help of Roch All●m, and a Tincture of Copper. And according as the Weight in Oil of the Body proposed, recedes more or lesle from the Weight of the Standard, so the Adulteration may be probably concluded to be lesser or greater. CHAP. XI. BEfore I go of from this Subject, 'tis fit that I give you notice, that the hydrostatics may supply us with another Way of Estimating the intensive Gravity of Bodies, Solid or Fluid, that may on some occasions be of good use. The Way I mean is this; we take a solid Body more than heavy enough to sink in Water, and carefully observe, once for all, its Weight in the Air; than we weigh the self same Solid, first in One of the Liquors we would examine, and than in another; and so onwards, if there be more than two: And having noted the difference between the Solid, and each of the Liquors, 'tis easy to found, according to the Practice elsewhere delivered, the specific Weight of each, and the Proportions betwixt them. And in regard 'tis but One and the same Solid, that is compared to the differing Liquors; whatsoever their Number be, it will not be difficult, to compare the specific Gravities of those Liquors betwixt themselves, and to discover by the Weight of the First, That of any of the Others that One pleases. The proposed Way having been but Summarily delivered, it will not be amiss to subjoin some Remarks relating to it. And First, If you intent to employ but One Solid in your Examen of Liquors, 'twill be necessary you make Choice of such an one, as hath a much greater specific Gravity, than is necessary to make it sink in Water. For there are some Liquor● that are far, perhaps twice, more ponderous than This newly named. Secondly, The Body aught to be heavy enough to sink in all Liquors but Quicksilver, (for in That, none but Gold is ponderous enough to sink.) But if your Trials are to be made upon Liquors that belong to the Vegetable, or Animal, Kingdom, the Body you employ need not be near so ponderous; tho' it aught to be more so than Water, because (as I found by Trials purposely made) some Liquors, that are very Spiritous and Volatile, are yet much heavier in Specie, than Water. 'Tis not very easy to pitch upon such a single Solid, as may have all the Qualities in reference to our Purposes, that may be desired in it, if it be to be made use of for a long time. For Thirdly, Besides that, it aught not to loose of its Weight, (and consequently to change it,) by the insensible Avolation of Effluvia, and that it must be, as was freshly noted, of a considerable specific Gravity. Fourthly, It aught not to be too big, or too intensely heavy, jest it be too heavy for a tender Balance, or require too much Liquor to environ it. Fifthly, It aught to be of such a Texture as not to be dissolved, or corroded by any of the several Liquors, some of which may be sharp and piercing Menstruums, that 'tis to be weighed in; and those too of differing Natures. Sixthly, It should also be of such a Make, as is not easily liable to be broken, or otherwise spoiled, that it may last, till all the designed Experiments, tho' many, be made with it. Seventhly, and lastly, 'tis desirable, that it should be of a natural and uniform, as to Sense, and procurable Substance; that the Experiments, made with it, may be easily enough communicated to Others, and, if they think fit, tried over again by them; and that, if any be judged worthy, they may be transmitted to Posterity. Several Bodies there are, that I looked upon as more fit than most Others to be employed about the Trials, we are treating of. The chie● of these were Brimstone, Hard Wax Ivory, and White Marble. But though each of these, especially if fitly shaped, may be of use on some particular occasions; yet every one wanted some of the desirable Qualifications lately mentioned. And therefore, I made much more use of Three other Bodies, not because they were such as I could Wish; but because they were the least remote from being such, among those I could Procure. The first of these was a piece of Amber between Three and Four Drams in Weight, of an high Yellow Colour, but very Transparent, and of an uniform Texture and convenient Shape. This was judged fit to be employed, when we were to examine the lighter sorts of Liquors, such as common Water, Rain-water, etc. Wine, Brandy, rectified Spirit of Wine-Vinegar, and the Liquors drawn from it, Cydar, Beer, Ale, Urine, many Waters and Spirits destilled from Bodies belonging to the Vegetable, and to the Animal, Kingdoms. But 'tis not proper for the more ponderous kind of Liquors; since 'twill not sink to the Bottom, but float at the Top, not only of some Liquors of the Mineral Kingdom, (as will ere long appear;) but in several Liquors afforded us by the Saline parts of Bodies belonging to the Vegetable Kingdom; as you will found within a few Pages. The Second Body, I employed, was a Globular Glass, which I caused to be blown at a Lamp, and to be Hermetically sealed at the Neck, which was purposely made very short, after there had been Lodged in it as much Quicksilver, and no more, as we guessed would serve to sink it in any Liquor, except Quicksilver; This, by reason of its great Bulk, in reference to its Weight, was fit to discover Differences in Weight, minute enough between the Liquors 'twas weighed in; and 'twas out of Danger of being corroded, even by sharp Menstruums; and therefore, on divers occasions, I preferred this Instrument to any of the other Two; but 'tis disadvantaged by these Inconveniences, that 'tis difficult to be made, or procured, that 'tis hard to be preserved, being very easy to be broken, and that partly on this Account, and partly on Others, it can scarce be a fit Standard in reference to such Observations, as are to be communicated to Others, and transmitted to Posterity. Wherhfore for Experiments that are to be imparted & recorded, I made use of a Solid, which tho' heavier in Specie than was necessary to enable one to compare together the lighter sorts of Liquors, and to discover their minuter Disparities in point of Weight, is yet a natural Standard not subject to be broken without gross Negligence, nor to be dissolved, or corroded by the Liquors, 'twas to be immersed in, however of various Kind's, and very sharp, and ponderous enough to sink in all of them, except Quicksilver, and yet not near so ponderous, as the lightest Metals, or many Metalline Bodies; this Solid I speak of is Rock Crystal, which I formerly represented, as for its Purity, Homogeneity, etc. fit to afford a Measure, to which other Bodies may be compared in Weight, and by that means among themselves. And of this pure Concrete, we employed an almost complete Globe, (weighing in the Air ℥ ij ʒss Grains 3,) save that it had in one part of it two small Holes near one another, and easily stopped up with hard Wax, after there had been put through them an Horsehair, by whose means the Ball was easily fastened to the Scale from whence 'twas to hung in the Water. The bigness of this Globular Body made it the more fit to discover the lesser Differences between Liquors in point of intensive Gravity. But because we may have oftentimes occasion to know the Weight of Liquors, of which, by reason of their Preciousness, or Rarity, we can command but small Quantities, as it frequently happens, if we be to try the Weight of Chemical Oils, Tinctures, Essences, etc. We thought fit, for such Liquors, to provide a piece of Crystal, such as Nature had framed it, viz. an Hexagonal Prism, with a kind of Pyramid at the end, which is opposite to the extreme, at which 'twas broken of from the Body, it grew on. For this clear and finely shaped Crystal, (or, what is very near of kin to it, white Amethyst) by reason of its oblong Figure, might be commodiously weighed in so slender a Cylindrical Glass, as required but a small Quantity of Liquor to cover and surround a conveniently shaped Body, that weighed, in the Air, but half an Ounce and sixteen Grains. And to tender the Observations, made with these two Bodies of Medicinal and other Liquors, (for there are several of these Trials, that belong not to this Tract) the more useful to Experimenters, I shall here desire you to take notice once for all, that the Ball of Crystal was to Water of the same Bulk, as 2 57/100 to 1 or thereabouts; and the Prismatical Oblong piece of Crystal was to a Quantity of the same Liquor, equal to it in Magnitude, as 2 66/100 to 1. I have the more particularly delivered the Way of exploring the Gravity of several Liquors with one Solid, because there may be made of it a couple of Applications, that may, on several occasions, be of use, not only to Chemists, Physicians and Apothecaries, but to divers other Experimenters, that are not of either of their Professions. These Applications do, I confess, belong to another Paper, (viz. an Essay about some Uses of Chemistry improved) that was written divers years ago. But since, by reason of the loss of divers Leaves of it, I know not whether, much lesle when, 'twill come abroad, I shall at present borrow some few things of it to accommodate my present Design. First than, the piece of clear Amber formerly mentioned, or some such convenient Body, that is not too little, nor in Specie, too heavy, may serve the Chemist, Apothecary, and others, to make probable Guesses of the Degree of Spirituosity, or of Thinness, that is to be found in many Liquors belonging to the Vegetable, or the Animal, Kingdom; which may be done with far lesle Error by this Way, than by those uncertain Signs, on which the common Ways of guessing are want to be grounded. For having once provided a Liquor, by Comparison whereto One may safely make Estimates of Others of the same Kind, or Denomination, 'twill be easy, by observing the differing Weights of the Amber in several Liquors to judge of the Fineness of any of them in its Kind; for, Caeteris paribus, That is the thinnest, or abounds most in Spirituous parts, where the Solid weighs more than in the Other, as for instance, The Amber we employed, that in Water weighed 6 ¾ Grains, in common Read French Wine weighed 8 ½ Grains, in common Brandy of a pretty good sort, such as that of Nantz 1● 1/● Grains, and in vinous Spirits highly rectified 34 1/● Grains. The same Way one may employ, to judge of the Strength of Spirits of Vinegar, Acetum Radicatum, etc. but with a great difference in the Application. For it may pass for a general Rule, That, 'tis probable, that, of Liquors destilled from Wine, Cydar, Ale, and other fermented Liquors, the Hydrostatical Body (if I may so call it) weighs more or lesle, according as the Liquor 'tis weighed in, is more or lesle Spirituous; but, on the contrary, in Acid Spirits and Liquors, the lesle the Solid weighs, the stronger One may repute that Liquor to be: That greater Decrement of Weight proceeding usually from the greater Proportion, it contains, of Salts that are not Volatile. I must not here pretermit one Convenience of the Way newly proposed, that may, in tract of time, save you some Money, and, at lest, will enable you to Husband better, than in the vulgar Method you can, Liquors that you may have but small Quantities of, or that are worthy to be preserved. For, you know, 'tis usual with many Chemists, and especially those that are more circumspect than others, to try the Goodness of their Spirit of Wine, or Brandy, or other Spirits drawn from fermented Liquors, by setting Fire to a spoonful of the Spirit to be examined, in order to see, how much of it is totally inflammable, and how great, or little, a Portion of Phlegm will be left behind. But, not here to mention the Scruples I propose in another Paper, about this Way of trying Ardent Spirits, I shall now only take notice, that, by the newly recited Way, you loose or spoil all that you try, and the better the Spirit is, the greater is your Loss, whereas by the Hydrostatical Way, the Liquor is examined without being destroyed. 'Tis now fit to add, that, by the help of the foregoing Observations, One may also make Estimates of Liquors of the same kind not destilled, whether fermented or not fermented; as several Sorts of Beer, or of Ale, or of Cydar, or of Juices of Apples, or of Pears, newly pressed out. And the same Hydrostatical Solid may be employed, to compare with one another, in point of intensive Weight, Liquors of differing kinds, as Wine, Beer, Ale, Meads, Cydar, Perry, Verjuice, expressed Oils, Essential Oils of differing Bodies, etc. But, in case the Liquors to be employed be very ponderous, Amber will not be a fit Solid to be examined about them; for I have found by Trial, (what one would scarce suspect) not only that it would swim or float, in divers Liquors made by Solution of Salts, whether in the moist Air, or even in Water, such as Oil of Tartar per Deliquium, Solution of Salt of Tartar in as little Water as may be, and Solution of the Salt of Pot-ashes, etc. But some destilled Liquors would not suffer my pellucid Amber to sink to the Bottom, as I found by Trial made with Oil of Vitriol, with Spirit of Nitre, and even with good Spirit of Salt. Besides, there may be another Use made of our Hydrostatical Solid, which may, on divers occasions, be as Serviceable to Experimenters in general, by assisting them to proportion, to their purposes, the Strength of the Menstruums, and other Liquors, they are to employ; as the former use is to Destillers and Apothecaries, for discovering the Strength of the already prepared Liquors, that they would examine. For there are divers Experiments, that either do not succeed, or, at lest, do not succeed so well, unless the Menstruums, or other Liquors, employed in making them, be of a determinate Degree of Strength, (which is usually knowable by a certain Degree of intensive Weight.) This will be the more easily granted, if (as I have elsewhere shown) the Strength and Spirituosity even of some Liquors, whose chief Virtue and Use is to be good Solvents, may yet be unfit to dissolve, as well because their Strength exceeds a certain Measure, as because, by their Weakness, they fall short of it; Of this, I remember, I gave an Instance in Aqua Fortis, whose strength, as it's Name intimates, is reckoned the best Quality it can have; for I found, that if it were rectified so much as to make it as strong, as we could, or but somewhat lesle strong than that, it would not dissolve Silver, but required to be weakened by an Addition of Water; and I found, that the Menstruum, tho' it were not much rectified, would not near so well dissolve the Filings or Rasping of crude Lead, when 'twas moderately strong and fit to dissolve Silver, as when 'twas allayed with a considerable Quantity of Water, especially if afforded by Rain, or by Distillation. I shall add, that, in making Extractions from many vegetable Substances, for Medicinal Uses, Chemists themselves may fall into a Mistake, when they affect to employ their most rectified Spirit of Wine, as the best Menstruum for their purpose: For the Medicinal Virtue of not a few such Bodies does not reside only in what Chemists call their Sulphur, and might perhaps more properly be called the Resinous Part, which indeed is best dissolved by such Spirit of Wine, as is carefully dephlegmed; but also in a more Gummous, and, partly perhaps, almost Mucilaginous Substance, for whose Extraction a moderately Phlegmatic Spirit is more proper; because of the Aqueous Portion, that is mingled with the inflammable One; since we see, that some Gummous Bodies, as Gum Arabic, Gum Tragacanth, etc. are not disposed to be dissolved by the best rectified Spirit of Wine, as they are by Aqueous Liquors, as Water, weak Spirit of Wine, etc. and some, tho' dissoluble in both kinds of Menstruums, are yet lesle easily so in strong Spirit of Wine, than in waterish Menstruums; as may be observed particularly in Myrrh; for other Instances applicable to these Advertisements belong to another Paper. And what has been now said, may serve to persuade you, that it may be of good use, on divers Occasions, to take Notice of the Degree of Strength of the Menstruum, or other Liquor, we employ about this or that nice Experiment; that when we have occasion to reiterate it to the same Purpose only, we may be able to bring the Liquor we make use of to the same Degree of Strength with That, which we formerly emyloyed, and by which the designed Effect was produced. But, in Experiments that should be very Critically made, 'twill not be amiss to bear in mind this Caution, that if the Liquor be very ponderous in Specie, as Oil of Vitriol, or Oil of Tartar per del quium, 'twill be fit to put something into the Scale, from which the Solid hangs, to make Compensation for that part of the Hair that is immersed, since Horsehair not being of the same Specific Gravity with this Liquor, (tho' it be presumed to be so with common Water) is to be considered, as a somewhat lighter Body, capable of buoying up the Solid a little; and therefore its Comparative Levity should be compensated. CHAP. XII. BEsides the Way, we come from discoursing of, there is indeed another Way, which we have, on divers Occasions, found useful, to compare different Liquors, that are of the same Magnitude, in point of Weight. This is done by successively filling a Vial greater, or smaller, furnished with a pretty long and slender Cylindrical Stem, to a certain stable Mark made near the Top, with the several Liquors to be compared together in point of Gravity. But this Way I must here do no more than name, not so much because I speak of it in a convenient place of another Paper, as because 'tis not Hydrostatical. But there is also another Way to discover, Whether or not, Two, or more, Liquors proposed differ in Specific Weight, and to make some, not groundless, Estimate of their Differences. This is done by a hollow Cylinder of Brass, or other Metal, made somewhat heavy at the bottom to make it swim upright, that sinks more, or lesle in several Liquors, as they are lighter, or heavier, one than another. But the diligent Mersennus himself, who proposes this Way, confesses it to be very difficult to make sure Observations by it. To which, I shall therefore add but this, that, being a Metal, it may be corroded by Acid Menstruums, and if it be of Brass, or Copper, it may be wrought upon or injured by Urinous Menstruums, too. What Mersennus said of this Instrument, may be applied to another, tho' differing from it, both in Shape and Matter. For 'tis made of two Glass Bubbles, and a very slender Stem, which is Hermetically Sealed with a Ballast in the lowermost of Quicksilver, to keep it steady, when partly immersed in Liquors, in which this Instrument, like the Metalline Cylinder, sinks deeper in lighter Liquors, than in heavier, in a measure somewhat answerable to their Differences in Gravity. But, tho' I have, on several occasions, employed these Instruments, and found them not unuseful, when I did not confine myself to One, or Two, but made use of several of different Sizes, according to the various Liquors, I was to examine; yet what you may elsewhere found about this Instrument, dispenses me from saying any more of it in this place, than that, for some of the ends aimed at in this Chapter, it is inferior to the Way of examining Liquors by the help of the Balance. There is also another Way, that is Hydrostatical, proposed by Mersennus, of weighing of Liquors in Water, and it is This; He bids you take a Glass Vial, to which, being first weighed in Air, and than in Water, you are to adjust a Stopple of Wax, or Cork, that will fit it exactly. This done, you are to fill the Vial with the Liquor you would examine, so that no Air be left between it, and the Stopple. The Vessel thus filled, you are to weigh in Water, and subtract from its Weight there, the formerly noted Weight of the Glass itself in Water, and also That of the Stopple; which done, the remains will give the Weight of the Liquor proposed in Water. This Method I lately chanced to found propounded by (the Writer newly named) the industrious Mersennus in his Hydraulicks; but, I remember not, that he affirms himself to have made use of it; And tho' it may be serviceable on some occasions, yet, I fear, it will be troublesome in Practice. For, (to omit some inconvenient Circumstances) ordinary Vials, capable of containing a competent Quantity of Liquor, are, usually, too heavy to be employed with tender Balances; and common Stopples (such as Mersennus may be well supposed to have employed) will be subject to divers inconveniences; as, that they may be penetrated by some Liquors, and corroded by others, and if they be made of Cork, or of common Wax, or any other Substance lighter, in Specie, than Water, 'twill not be easy to found its specific Gravity; especially since Evaporation, and other Accidents make this itself vary; and whatever Matter, Vegetable or Animal, it be made of, the Vessel will cost you two Operations, One to discover the Weight of the Vessel in Water, and the Other that of the Stopple, (at that time) which is troublesome. Wherhfore, when I met with this Way in the ingenious Mersennus, it seemed to me more inconvenient, than One, that, I remember, I had formerly thought of, and which I have sometimes put in Practice, by choosing a Vial not too large, and of a round Figure, that being the most capacious under such a Superficies, and, instead of other Stopples, fitting it with one of (the like) Glass, carefully ground to the Neck of it. For, by this means, the inconveniences of a Stopple lighter than Water were avoided, nor would the Stopple altar its specific Gravity, either by Imbibition, or Evaporation, nor would it be penetrated by the most subtle Spirits, nor corroded by the most fretting Ones. To which may be added, because, in some Cases, it may be considerable, that a Glass-stopple, as it will not be wrought on by the Liquor contained in the Vial, so it will not communicate any Tincture, or extraneous Quality, to the Liquor, which cannot be affirmed of a Stopple of Cork or Wax, in reference to some Subtle and very Corrosive, or otherwise very penetrating Liquors, this Hydrostatical Bottle (as for distinction sake I call it) being together with its Stopple carefully weighed, First in Air, and than in Water, (that the Gravity of the whole Instrument in that Liquor may be settled once for all) we filled it exactly with the Liquor to be examined, and so proceeded, as we if were to weigh Quck-silver according to the Manner formerly declared in the vl Chapter. The Weight of the given Liquor in Water being thus obtained, its Proportion in Weight to Water of the same Bulk may be easily discovered by the Way formerly delivered in the Second Chapter (or the Tenth Chapter.) This way of examining Liquors may, on some occasions, do good Service, and I did the rather, now and than, make use of it, because 'tis applicable to all kind of Liquors, whether heavier in Specie than Water, or lighter. If you lay aside the Stopple, the round Ball itself may be made use of, on several Occasions, instead of that Hydrostatical Bucket, formerly mentioned; for the weighing of Quck-silver, and divers heavy Powders; especially if they be Coarse Ones. But if the Instrument be fitly shaped, and not too heavy, there may belong to it a greater Conveniency than. This. For when you have, and are willing to spare, Liquor enough to environ the little Bottle, it may be usefully substituted to the Hydrostatical Bubble, with Quicksilver enclosed, that I formerly recommended. For, by reason of its exact Stopple, it has no need of an Hermetick Seal, (which is not easy to be be made or procured▪) and 'tis far lesle Subject to be broken, than a Bubble. And yet that which I most made use of, (and which weighed about ℥ i ʒii● ss. Grains nineteen, or 709 Grains) being well stopped with only Air in it, would link by its own Weight in Water, and in Liquors lighter than This, as Wine, Brandy, etc. And if it were to be employed in Liquors much more Ponderous than Water, as Aqua Fortis, Oil of Tartar perdeliquium, etc. 'twas easy to make it fit to be weighed in them also; by putting into it a Quantity of Quicksilver (or some other fit Body) of a determinate Weight, as two, three or four Drams, before we stopped it: Which Ballast, when the Operation is over, may, if it be Quicksilver, be easily taken totally out, and kept apart for the like Uses: and the empty Bottle, and Stopple, may thereby become fit again, to be weighed in Water and lighter Liquors. But notwithstanding all this, because Glasses, for size, shape, and weight, fit for Balances, tender enough, and furnished with Glass Stopples exactly fitted to them, are very difficult to procure; and the Way itself is subject to some of the Inconveniences, that we imputed to other Ways not long since mentioned: it seems, that, generally speaking, See the Chapter. this Way of finding the Weight of Liquors in Water, is Inferior for common use, to those more simple Ones, that we formerly recommended. CHAP. XIII. Use VI. HAving now laid down the Method of weighing one Liquor in another, 'tis allowable, and may be fit, that we subjoin some Application of it: Especially, because it will become me to make good, in some measure, what, I remember, I formerly hinted to you, viz. that, in the subsequent part of this Paper, there would be delivered a further Use, which may be counted the VIth. of the hydrostatics in examining Medicinal Bodies. And tho' by the Instances we lately had occasion to propose in some of the Chapters preceding This, divers things referable to this Use, are set down already; Yet I should not content myself, (as I now must do) to point at the chief Heads or Kind's of things referable to it; if, on a Subject that is more fertile, than it seems, want of leisure did not restrain me from descending to treat of the particular Instances, that belong to them. Among the Services than, that the hydrostatics may do a sagacious Physician, I must not omit One, tho' it has not hitherto, that I know of, been propounded by any Author. And, I hope, you will not think it improper to be taken notice of here, tho' it do not regard only the Materia Medica, but is applicable (as I may elsewhere relate that I made it) to divers Subjects, that are referable to other Parts of Physiology: Since divers Bodies, that seem not so directly to regard the Materia Medica, as 'tis usually reposited in the Shops of Drugster's, have been, in some times and places, and may deservedly be now made to afford Matter for Remedies, to a free and ingenious Physician. I consider than, that there are many Liquors, whose specific Gravity it may be useful to know, not only, as it may help to distinguish Genuine, or well conditioned Ones, from Them that are not so, but for other good Purposes too. Instances of this kind may be afforded by the Juices of Herbs and Fruits; where (according to the Direction given in the last Chapter) we first weigh a determinate Quantity, as an Ounce, or so many Drams, in our Hydrostatical Jar, or Bucket; and putting some Oil of Turpentine on it, we sink it warily into that Liquor; whose specific Gravity in reference to refined Silver, clear Rock Crystal, (or some other Body, if we know it to be as pure) has been carefully found out and registered: For, by this means, (as we have lately manifested) substituting this Oil for common Water, we may discover the specific Gravity of Liquors, not to be weighed in Water, because they mingle with it. And thus we may found, not only the difference in Ponderosity between the Juices of Plants of differing kinds, as of Wormwood and Roses, and sometimes of the subordinate Species of the same Genus, as of Absynthium Vulgar, Ponticum, Romanum, etc. and Roses White, Read, Damask, Yellow, etc. but we may on some occasions observe, whether, and, if at all, how far, the keeping of a Juice for some time, more or lesle, or the Fermentation of it, or the Putrefaction, will altar its specific Gravity. There are also other Liquids used by Physicians, and not ponderable in Water, that may be by this Way examined, as Honey, Vinegar, Verjuice, etc. And by the same Way may be also discovered and compared, the specific Weight of the Juices of Fruits of different kinds, as of Grapes, Apples, Pears, Quinces, etc. and of subordinate Species belonging to the same Genus, as the newly expressed Juices, that make Sacks, French-wines, Rhenish-wines, etc. and those Liquors, that are pressed out of several sorts of Apples, as Pippins, Pearmains, John-Apples, Queen-Apples, etc. And in divers of these, a Person that is curious enough, may probably, by the Method we have been proposing, be enabled to take Notice of the Differences produced in the specific Gravity (whose Changes are usually accompanied with those of Consistence, etc.) in the several successive States, wherein the Liquors may be found at different times; as (not to mention the Juice of unripe Grapes, viz. Verjuice) the Juice of ripe Grapes is in very differing States, when 'tis newly pressed out; when it gins to ferment; when 'tis yet but New Wine; when it has attained its full Maturity and Perfection; when it gins to degenerate into Ropy, pricked Wine, etc. and when 'tis absolutely changed into Vinegar, or else into Vappa. But here it aught not to be concealed from you, That in this kind of Experiments, to make use successfully of the Hydrostatical Bucket is a Task difficult enough, for Reasons that a few Trials will easily discover. And therefore, tho' I would not discourage the Skilful, yet for those that do not found themselves dextrous at making Experiments, I think it adviseable to employ, instead of the Bucket, Amber, or some other convenient Hydrostatical Solid, or rather (which is better) a Glass-bottle and Stopple, such as We formerly described; but as large, as may well be employed without over-loading, or injuring, the Balance. CHAP XIV. AS I thought 'twas fit to give the foregoing Advertisement, by way of Caution, in the Cases that occasioned it; so having considered the Nature and Scope of the Hydrostatical Experiments in General, that belong to this Essay; I shall venture to add for the Encouragement of those, that are better furnished with inquisitive Minds, than with nice Balances; that tho' in divers Trials, especially Those that are made about precious things, as Gold, Pearls, Diamonds and other Gems; there is no relying upon any, but very Good and tender Balances; Yet, on many other occasions, 'tis not necessary, tho' it be desirable, that the Scales, we employ, should be extraordinary Good. And this for two Reasons: First, because many Hydrostatical Experiments are such, that a little Variation from the exact Proportion of the Solid to the Liquor, or between Bodies of the same Denomination, can lead us into no considerable Error; or, at lest, not defeat the Experimenters main Design; as, with a Balance that is not nice, One may sufficiently distinguish between an human Calculus, and a Pibble, or other ordinary Stone; and between Course and Fine, native Cinnabar: And between a true Guinea, or other piece of coined Gold, that is not very small, and a sergeant One, of Brass, or any such mixture, tho' never so finely guilt. And Secondly, Because, as there are few Physical Experiments, wherein Mathematical Preciseness is necessary, and fewer wherein 'tis to be expected; So in many Hydrostatical Trials, 'tis very probable, that the difference of Bodies of the same kind, or Denomination, flowing from their Compositions, and internal Textures, will make a discernible, tho' but small, difference in their specific Gravity: As, in Rock-Chrystal itself, we have found some pieces to be to Water, as 2 1/10, or a little more, to One; and others, to be to the same Liquor, as Two and Six, or between Six and Seven Tenths to One. And therefore, how exact soever the Balance be, there must be some Allowance made for the diversity, that may be found in the Bodies themselves, that are examined, which diversity may perhaps produce, at lest, as great a Difference in the Proportions we seek for, as needs to be expected from a small Difference of tenderness, in the Balances we employ. And indeed, neither One of those Differences, nor the Other, (nor perhaps Both together,) is want to be so considerable, as to challenge much regard in Physical Experiments; or at lest, as to hinder it to be true, that, on most occasions, the Hydrostatical Way of examining the specific Weight of Bodies, is preferable by far to any other Way of doing it, that has been Practised. Before I proceed to the remaining part of this Essay, it will be worth while to obviate an Objection, that I foresee may be made by Critical Naturalists, against the Method hitherto delivered, of finding the Proportion in Weight, betwixt a sinking Body, and Water of the same Bulk. For it speciously may, and probably will, be objected, that, by this Method, we cannot discover the Proportion between a Solid Body, and Water in General; but only betwixt the proposed Body, and the particular Water 'tis weighed in; because there may be a great Disparity between Liquors that are called, and that deservedly, common Water. And some Travellers tell us from the Press, that the Water of an Eastern River, which, if I mistake not, is Ganges, is by a Fifth part lighter than our Water. But to this plausible Objection, I have Two things to Answer. And First, having had, upon several occasions, the Opportunity, as well as Curiosity, to examine the Weight of divers Waters, some of them taken up in Places very distant from one another; I found the difference between their specific Gravities far lesle, than almost any Body would expect. And if I be not much deceived by my Memory, (which I must have recourse to, because I have not by me the Notes I took of those Trials) the difference between Waters, where One would expect a notable Disparity, was but about the Thousandth part (and sometimes perchance very far lesle) of the Weight of either. Nor did I found any Difference considerable, in reference to our Question, between the Weight of divers Waters of differing kinds, as Spring-water, River-water, Rain-water, and Snow-water, tho' this last were somewhat lighter, than any of the rest. And having had the Curiosity to procure some Water brought into England, if I much mis-remember not, from the River Ganges itself; I found it very little, if at all lighter, than some of our common Waters. And now I shall represent in the Second place, that I do not pretend, (and indeed 'tis not necessary) that the Proportion, obtainable by our Method, should have a Mathemacal Preciseness. For in Experiments where we are to deal with gross Matter, and to employ about it material Instruments; 'tis sufficient to have a Physical, and almost impossible to obtain (unless sometimes by Accident) a Mathematical Exactness; as they will scarce deny, that have, as I have done, considered, and made Trial of the Difficulties, that oppose the Attainment of such a Preciseness. CHAP. XV. Hydrostatical Stereometry, Applied to the MATERIA MEDICA. SECT. I. THere is an Use of hydrostatics, which tho' it do not directly tend to the Examen of Drugs, or Simples received into the Materia Medica, yet may be Serviceable both to the Physician and the Naturalists, in delivering their Descriptions; and so it may indirectly conduce to the knowledge of them; and help, on some occasions, to distinguish between Genuine Simples (especially Fruits) and those that are not so; 'Tis known, that the Writers of the Materia Medica are want to set down the Bigness of the Bodies they describe, by very uncertain Guesses; and those that, to be more accurate, assign them determinate Measures, are want to do it, by saying, that such a Fruit, or other Body, is, for Example, an Inch, or two Inches, or half a Foot long; and half an Inch, or a whole Inch, or two Inches and an half, in breadth. But 'tis obvious to those that are not great Strangers to the Mathematics, that, according to this Way of describing Bodies, there may be, by reason of the great Variety of Figures, especially irregular Ones, they are capable of, a very great Disparity of Magnitude, or Bulk, in Bodies, to each of which, the same Length and Breadth may belong or be applied. I should here be able to present you an Hydrostatical Way of determining the Bulk of Bodies, both much nearer the Truth, than that newly recited, and grounded as well on Experiments as Mathematics; if among other Papers, I had not unfortunately lost One, that I wrote many years ago, about the measuring of Solids, by the help of Liquors. But tho' I cannot, out of my Memory, recover the Theoretical part of that Writing, (whose Loss I regret, because it had been examined by One of the exactest, as well as famousest, Mathematicians of our Age, whom I invited to be present at the chief Experiments) yet, I think, I can call to mind as much of the Practical Applications of it, as may suffice for my present purpose. The ground of the Way, I am about to propose to you, will be easily understood by the following, tho' but short, Account. I caused to be carefully made by skilful Artificers several Cubes, both of different Sizes and different Materials, as Marble and Metal; whose sides were each of them, as near as the Artist could make them, either an exact Inch, or precisely more Inches than One, according to our English measure; which is said to differ very little from the correspondent One of the old Romans. These Cubes were carefully weighed in trusty Balances: First, in the Air, and than in common Water. And tho' I found some little (and but little) difference, between the Products of the Trials; yet that Difference being no more than might reasonably be expected from the scarce avoidable Imperfection, even of good Artists and their Tools; We concluded, that One might, without any considerable Error, take a Medium (as they speak,) between these Products, and allow even to this Medium, a Latitude of some Grains; since that Latitude will not amount to the Sixtieth part of the Weight of a Cubical Inch of Water. Since therefore some of our Trials inclined us to judge, that about Two hundred and sixty; and some others to think, that about Two hundred fifty two; and others again, that about Two hundred fifty six, came nearest to the true Weight of a Cubical Inch of Water; we thought ourselves at liberty to make use of that Number, that should appear most commodious for Practice, by reason of its Divisions and Subdivisions into Aliquote Parts; Especially if the Body to be examined were not great; since, in that Case, Two or three Grains more or lesle would not be considerable, especially in a Physical Experiment, where Geometrical exactness is not to be expected, nor indeed required; and a far lesle accurate Estimate will be lesle unaccurate, than can with any certainty be made by the formerly mentioned Way of judging, by the Length, Breadth, and Depth (or Thickness) of the Body proposed. I made the lesle Scruple to pitch upon the last of the Three forementioned Numbers of Grains, not only, because it affords many Aliquote parts for a Number that is no greater, since barely by a successive Bipartition, it affords Seven such Parts, viz. 128.64.32.16.8.4. and 2; But, because I was encouraged by an Experiment differing from those already mentioned. For, having caused to be purposely made by a good Artist, an hollow Cube of Brass, whose Cavity was fitted to contain a just Cubical Inch of Matter; (either Solid or Liquid,) we put it into one Scale of a tender Balance, with a just Counterpoise in the other, and placed it there, as Horizontally as we could. Than we warily put into it, little by little, as much common Water, as it would contain, without either overflowing, or having its Surface, manifestly turgid; putting also from time to time in the opposite Scale, small Weights to keep it from swerving too much at once from an Aequilibrium. And tho' it is extremely difficult in Practice, to discern with certainty, when the Vessel is so exactly filled, that a Drop, or even Two, or Three drops, more or lesle, cannot be added, or taken away, without being observable by the Eye; Yet, for this very Reason, we thought our Experiment agreeable enough to our Supposition, when we found, that by so light an Alteration, the Weight of the Water, when the Scales were heedfully Counterpoized, amounted to near about Two hundred fifty six Grains, which Number we shall therefore hereafter employ, as expressing the Weight of a Cubical Inch of Water. And now to apply the past Discourse to our present Purpose. Suppose, for Example, that a Solid, heavier in Specie than Water, having been weighed first in the Air, be found to loose of its Weight in the Water ℥ ss Sixteen Grains, that is, Two hundred fifty six Grains, I say, that the Dimensions of this Solid, if it were of a Cubical shape, would make it equal to a Cubical Inch: So that, (to express the thing yet more clearly,) if the given Body be supposed to be an easily fusible Metal, as Tin, or Led; and being melted to be warily poured into the hollow Cube formerly mentioned, and suffered to cool, it would just fill it and no more; and consequently be a Cube of Metal; whose Length, Breadth and Depth are equal to one another, and each of them to an Inch. For, as 'tis a Fundamental Theorem in hydrostatics; demonstrated Mathematically by Archimedes, and else where Physically by me; that a sinking Solid weighs less in Water than in Air, by the Weight of as much Water as is equal to the Solid in Bulk; and since we have lately shown by Experiments, that a Cubical Inch of Water weighs ℥ ss. 16.) Grains, that is, 256 Grains; it will follow, that when the Decrement of a Body's weight in Water is found to be 256 Grains, the Solid content of that Body is a Cubical Inch: Since an Aqueous Body weighing 256 Grains is equal in Magnitude, as well to the Solid propounded, as to a Cubick Inch of Water. And here it may prevent a Scruple, to observe, that, to make Bodies equal in Magnitude, it is not at all necessary, that they should be of the same Weight, or of the same Matter; as is evident in Bullets of Copper, Tin and Gold, cast separately and dextrously in the same Mould. For tho' they be equal in Bulk; yet the Bullet of Copper will be much, heavier than that of Tin; and the Bullet of pure Gold will be more than twice as heavy, as that of Copper. Whensoever therefore you meet with a Solid, ponderous enough to sink in Water, that being weighed in that Liquor loses ● Grains of the Weight it had in the All●● you may conclude, the Magnitude o● Bulk of that Body to be equal to a Cubical Inch; of whatever Matter it consists, not of what Shape soever, regular or irregular, it be. And in case the Solid proposed do (as it will very often hap) loose of its Weight in the Water lesle than 256 Grains; you may conclude its Bulk to be proportionably lesle than a Cubical Inch. And such is the Conveniency of the Number we have pitched upon, which abounds in Aliquote parts; that every 32 Grains, that the Solid loses of its Weight in the Water, answers to an Eighth (that is, half a Quarter) of an Inch in the Bulk of the Body: as, if the Decrement be 128 Grains, the Solid will be half a Cubick Inch; and if it be but 64 Grains, 'twill be but a quarter of a Cubick Inch; and so if it be 160 Grains, 'twill be ●/●, that is, half and half a quarter of an Inch Cube: and on the other side, if the Decrement of the given Body exceed the Standard, viz. 256 Grains, twice, thrice, etc. than that Decrement being reduced to Grains, as suppose it weigh ℥ i + Grains 32 (amounting to 512 Grains;) or ℥ i ss + Grains 48 (amounting to 768 Grains) the Body will be equal to two or three (single) Cubical Inches. And if, after the Division there remains a Fraction, 'twill not be difficult to estimate it, to him that considers what has been newly delivered. SECT. II. TO discover Hydrostatically the Solid Contents of a Body heavier in Specie than Water; to him that knows how to make use of the Method newly delivered, 'twill not not be very difficult. But to measure, by the help of Water, the Solidity of a Body lighter in Specie, than that Liquor; is a work not so easily performed. It may somewhat lessen the Difficulty, to premise, that there are two sorts of Bodies, that will naturally not sink in Water. For some are of a closer Texture, and will not be easily invaded by that Liquor; at lest, in so short a time, as they are of necessity to be kept in it: and others abound with Pores, that dispose them to imbibe the Water, they must be kept immersed in, till the Experiment be dispatched. To begin with the First sort of Bodies: 'Tis known to Hydrostaticians, that, according to a Theorem of Archimedes, the weight of a Body belonging to that kind, may be gathered from the weight of the Water, that is equal, in Magnitude, to that part of the Body, that is immersed in that Liquor, when the Solid floats freely upon it; as, if a Paralelipipedon, or a Cylinder, of Wood, 12 Inches long, being placed upon Water, should rest there, when a 12th part of it lies beneath the Surface of the Liquor; in this case, the Weight of the Water, equal in Bulk to that immersed 12th part, would be equal to the weight of the whole wooden Body. But because the Bodies, whose Bulk Physicians and Chemists may have occasion to Examine, will very seldom hap to have Shapes so near those of regular Ones; 'twill scarce be worth our while to enlarge upon this Way of Estimating light Bodies; which 'twill be so troublesome to make fit for most men's Practice, that, unless it be desired, I shall not trouble you with it; but forthwith proceed to what will conduce far more to our present Design, which being, To measure the Solid Contents of Bodies, not so heavy (intensively) as Water, and for the most part irregularly shaped; It will be necessary, that we employ a Method differing from what we have hitherto made use of. In the First step of this, tho' not in the Second, we may be helped by the industrious Mersennus: Who probably borrowed his Way of Ghetaldus, from whose Promotus Archimedes, he professedly borrows many things. But because, that, on this occasion, Mersennus, affecting Brevity, hath made himself obscure; so that what he writes can scarce be understood, but by Mathematical Perusers; I shall, for the sake of another sort of Readers, deliver the propounded Method, tho' not in so few words, yet more clearly, and orderly: First than, you shall weigh in the Air, the Body, (lighter than Water) to be examined: Secondly, you shall take a Place of Led capable of making this Body sink with its self in Water, and of some Weight not encumbered with Fractions, as just a Dram, half an Ounce, an Ounce, etc. Thirdly, you must weigh this Plate in Water, and by substracting its Weight in this Liquor, from what it weighed in the Air, you must obtain a Difference, which will give the weight of as much Water, as is equal in Bulk to the immersed Lead. This, for distinctions sake, may be called, The specific Weight of the Lead in Water. Fourthly, you must tie together (which you may best do by One or more Horsehairs,) the Plate of Lead, and the lighter Body, and note the Weight of the Aggregate; which, as you know, is nothing but the Sum of the respective Weights of the lighter, and of the heavier, Body. Fifthly, you must weigh this Aggregate in the Water, and subtract its Weight in that Liquor, from the Weight that the same Aggregate had in the Air; and the Difference will be the Specific Weight of the said Aggregate in Water. Sixthly, From this Difference, subtract the formerly found Specific Weight of the Plate alone in Water, and the Remains will give you the Weight of the lighter Body in the same Liquor. Thus far our Author; without whose help, we may easily dispatch the rest of our Work, by the Method employed already of measuring Solids heavier than Water. For the lately obtained Weight of the light Body in Water, being, (according to the Method formerly proposed,) divided by 256 Grains, will give you the Solid content of that naturally floating Body. But because a Method, that is difficult enough to be put in Practice by those that are not more than ordinarily well versed in hydrostatics, requires to be illustrated by an Example; I shall subjoin an Experiment, that may serve, not only to clear up this Practice, but, in good measure, to confirm it too; We took than a piece of Oak conveniently shaped, and that weighed in Air, 193 ½ Grains. To this we tied with an Horsehair, a Plate of Lead weighing just half an Ounce, i e. 240 Grains. But before we tied them together, the Lead was weighed in Water, where it lost of its former Weight 20 Grains, which, being deducted out of the 240 Grains lately mentioned, left a Difference or residue of 20 Grains, for the Specific Weight of this piece of Lead, (For I have seldom found Led quite so heavy) in the Water. Than the Aggregate of the Wood and Lead was weighed: First, in the Air, and found to be 433 Grains and an half, and Than in Water, where it amounted but to 162 Grains; which being substracted from the Aggregate of the same Bodies in the Air, the Residue, or Difference, was found to be 271 and ½ Grains: From which Difference, the other Difference of 20 Grains (which had been lately found) of the Leaden Plate alone in the Water, being deducted, there remained 251 Grains and ½ for the Weight of Water equal in Bulk to the given piece of Wood If this number had amounted to 256 Grains, of which it fell short but 4 ½ Grains, we might have concluded the Solidity of it to be a Cubick Inch; since 256 Grains of Water, which we formerly found equal to a Bulk of Water of a Cubick Inch, was also now found equal to the Bulk of the given piece of Wood And indeed, intending (as I formerly intimated) to give an Example, that should not only Illustrate, but Confirm, the proposed Practice; I caused the Wood I employed to be form into as exact a Cube of an Inch every way, as I could procure from a Joiner, that bragged of the Pains he had taken about it: So that the Difference of its Weight in Water from 256 Grains, the Weight of a full Cubick Inch of that Liquor, may probably be imputed to some little Imperfection in the Figure of the Wood, or some other light Circumstance, not considerable enough to be much regarded. Of this Experiment one of my Notes gives the following Account. I. The Oaken Cube in Air weighs (ʒiiis Grains xiii ½.) 193 1/●. II. The Weight of the Lead in Air, (ʒiv.) 240. III. The Weight of the Lead in Water (ʒiiiss Grains x.) which, being substracted from its Weight in Air, leaves for its Specific Weight in Water 220. 020. iv The Aggregate of the Two in Air is 433 1/●. V The weight of both together in Water, is— Which being substracted from its Weight in Air, gives the Difference of both the Aggregates, 162. 271 ½. VI The Difference between the weight of Lead alone in Air, and in Water, or which is all one, the Specific weight of the Plate alone, viz. being substracted from the Difference of the weights of the Aggregates in Air, and in Water, gives [for the weight of the Cube proposed,] 020. 251 ½. The Way of measuring Bodies, that has been hitherto delivered, is appropriated to such, as will not at all, or, at lest, will not readily, be dissolved in Water. But because there are divers other Solids, as Lumps of Salt, Alum, Vitriol, Sugar, etc. whose Magnitudes it may be fit for inquisitive Men, of more Professions than One, to know, and to compare; I shall to what has been already said, subjoin this Advertisement; That the same Way may be applied to measure the Magnitudes of Solids dissoluble in Water, if, instead of this Liquor, we substitute Oil of Turpentine; whose Proportion, and Specific Gravity to Water, we have found, or is otherwise known to us. When I first made this Reflection, I had not such Conveniencies, as when I found the weight of a Cubick Inch of Water, to determine the weight of a Cubick Inch of Oil of Turpentine. But, having yet lying by me the hollow Vessel of Brass, whose Cavity was an exact Inch, that I employed to found out the weight of a Cubick Inch of Water; I made use of it on this occasion too: and found that, when it was carefully filled with such Oil of Turpentine, as we were want to employ about Hydrostatical Experiments; the contained Liquor amounted but to 221 Grains, and an Eighth (part of a Grain;) by which number the Difference of the weight of a Solid in the Air, and in that Oil, being divided, the Quotient will give you the Solid Contents of the examined Body. After so circumstantial an Account, as we have given, of the Way of Hydrostatically examining such floating Solids, as, like the Wood we employed, are of a Texture at lest moderately close; it may be seasonable, to proceed to the mention of the Second sort of floating Bodies, that I formerly told you might be proposed to be weighed in Water: Namely, such as, by their Porosity or Laxeness of Texture, are subject to imbibe too much of that Liquor; even in as little time as is necessary for the dispatch of the Experiment. In his Phaenomena Hydraulica, pag. 185. Mersennus (more briefly than clearly) proposes an Expedient in this case, which is to cover over the Body to be weighed in Water with Wax, Pitch, or some other Gluten, as he calls it, whose Specific Weight in Water must be first known. But, I take Bees-wax to be much preferable to the other Two. For Pitch is so apt to stick to Ones Hands or clothes, that 'tis troublesome to apply it, and very difficult to get it of: And as for Glues, most of them, especially the more common, are dissoluble in Water, and therefore not so fit for the purpose as Bees-wax, (for That, I presume, he means by Wax;) which has this Conveniency in it, that its Proportion to Water being usually constant enough, and the Gravity of those two Bodies differing but little, one may more easily dispatch a good part of the Experiment; which is thus to be performed. Take the Solid (lighter than Water, that you would examine Hydrostatically, and having weighed it in the Air, over lay it carefully with a thin Coat of Bees-wax, so that no part of it may remain uncovered, or accessible to the Liquor. Than take also in the Air the Weight of the Wax you have employed, and fasten to the Body thus coated, a Plate of Lead, or Tin, heavy enough to make it sink, and observe the weight of the Aggregate in Water. This done, subtract the weight of as much Water, as is equal in Bulk to the Wax, and proceed with the rest, as is before taught. Mersennus declares this Practice by this Instance, if the Wax that invests the proposed Body be of ℥ xxij in the Air, the Bulk of Water equal to it will be ℥ xxi; and therefore a Quantity of Water of ℥ xxi, must be first taken away, or substracted, that the remaining Bulk, equal to the (immersed) Body, may, by its Gravity, show the Gravity of the Body (proposed,) as has before been said. But, because the Way, above delivered, can help us but to the knowledge of the Weight of the proposed Body in Water; we must, to discover the Solid Content of it, proceed further than our Mersennus enables us to go; and therefore we must divide the Weight of the Solid in Water, already found, by 256 Grains, that by the help of the Quotient we may obtain the Solid Contents of the proposed Body. I have sometimes (to add That upon the By,) thought of, and tried, another Expedient, to hinder smaller Solids, whether lighter or heavier in Specie than Water, from imbibing the Ambient Liquor. In order to this, I first found the Weight of a Cubick Inch of Quicksilver, (which is not difficult to discover by its Proportion to Water of the same Bulk.) And than we brought the Body to be measured, into a Vessel, whose Solid Contents were known before; and Thirdly, all that was not possessed by the firm Body, being filled with Quicksilver, 'twas easy enough to know by the Difference in Weight of That Quicksilver, from the Weight of the Quicksilver, requisite to fill the whole Vessel, to how much Quicksilver the environed Body was equal. And by this means, and the knowledge before gained of the Weight of a Cubical Inch of Mercury, the Solid Contents of the Body proposed was not difficult to be obtained. But I forbear to give more than this Intimation of an Expedient, which, besides that it belongs properly to another Essay, is rather Mechanical than Hydrostatical. And for the same reason, I forbear to set down one Way of measuring the Contents of Irregular Solids, delivered in some Books of Practical Geometry; and another, but yet unpublished, Way, differing enough from the Former, that tends to the same purpose. CHAP. XVI. BUt, I perceive, that 'tis now more than time, that I should put an end to a Labour, that has, I fear, tired you, because, I am sure, it has tired me. And yet I dare not conclude this Tract without briefly answering a couple of Questions, that, I foresee, may justly enough be asked me by a Peruser of the foregoing Essay. And first, I presume it may be demanded, Whether I have proposed the best Ways that can be thought of, to examine Bodies Hydrostatically? To which Question I answer, that, upon divers Considerations, some of which have been mentioned here and there in the Body of the foregoing Essay, I did not think myself obliged solicitously to Invent, or propound, new Instruments for the Hydrostatical Examen of Bodies. For tho' I am not Ignorant, that divers more curious and Artificial ways of finding out their Weight in Water, or their Solid Contents by it, may be devised by Persons more skilful and sagacious than I. And tho' also I think it not unlikely, that, when the Utility of such Practices comes to be taken notice of, Artificial Instruments will be found out to Facilitate, or otherwise Improve them: Yet, I thought it became me at first to propound only the more simple Ways of Operating, as the most likely to invite the Generality of those, for whose sake this Essay is made public; and to require, for the main part of our Experiments, only the Use of the Balance, as an Instrument easily procurable, and already, for other purposes, in most men's hands, without mentioning, at this time, any more Artificial Instruments; tho' some of them are such, as I have long since not only had thoughts of, but, for my own Uses, practised; which Intimation may be countenanced, if it were needful, by the mention of that little Instrument, for distinguishing between true and sergeant Guineas, or the like Pieces of coined Gold, by the help of Water; which was several Years ago published in the Philosophical Transactions, and has since (without staying for my Improvements of it) been made Use of by Some, and usurped by Others. But of such things, not more in this place. Having answered the First Question, it remains, that I consider the Second, wherein tho' I shall aim at Brevity as much, as in the former, yet I fear, I shall not be able to discuss it in as few Lines, as I did That. I presume than, it will be asked, What Credit may be given to the Estimates of the Weight, and Proportions of Bodies, obtained by Hydrostatical Trials? Since, we see, that tho' Mathematicians, not knowing, or not applying, our Observation about the Specific Gravity of Rock-Chrystal, and the Nature of Oil, especially that of Turpentine, have given us but the Proportions of Metals, and some very few other Familiar Bodies, as the Loadstone, Wax, Honey, Oil and Wine; yet those few that have not transcribed from one another, differ in the Tables, they have left us, of the Comparative weight of those few Bodies. This Question is so comprehensive, that, I think, it cannot well receive a single Answer; and therefore, I shall offer Two things to be considered about it. And first, I freely acknowledge, that there is no exact Uniformity in the Observations delivered about the weight of Metals, a●d the other Bodies newly named, among the few Authors that have written of this Subject; and there would probably have been yet more Difference in their Accounts, if some, even of those Writers, had not avowedly made use, to their purposes, of as much as they thought fit of the Tables of Ghetaldus. Nay, I shall not think it very strange, if I found, that the Experiments of the same Man, made at distant times, and in other differing Circumstances, should not all of them exactly agreed. For I have already noted, and, I think, in more places than One, that there will scarce be found so great an Uniformity in Qualities, and particularly in Specific weight, among Bodies of the same Kind or Denomination, as there is generally presumed to be. There may be also some Difference, tho' but little, betwixt the Water's Men employ, especially if the Air be at One time (as in July) intensely hot, and at Another (as in January) exceeding Cold. The Difference also of Degrees of Goodness of the Balances, Men employ about nice Experiments, is not altogether inconsiderable. But there is a thing of greater Moment than this, towards the hindering Hydrostatical Experiments, and even Statical Ones themselves, from being so accurate, as those, that are not versed in such Matters, may require. The thing I mean, is, the Difficulty of finding an exact Uniformity in Weights of the same Denomination, which, for that Reason, are vulgarly supposed to be exactly equal; But, to know how far this Supposition is to be relied on, it may at present suffice to set down some Passages of a Mathematician justly famous for his diligence, and who has made it his particular Work to examine these Matters scrupuolusly. The first Passage, I shall allege out of his Writings, shall be the short Account he gives of many Trials he made of natural Grains, whence all sorts of weights have been deduced. In Praefatione ad Librum de Mensuris, ponderibus & nummis. Cùm (saith he) omnia grana, vel semina, quae reperiri solent in atriis venalibus Lutetiae, ad Stateram expendissem, vixque granum ullum inter ejusdem speciei grana grano alteri exacte respondisset, in incertis ludere nolui. The same Author informs us, that the Roman Grains differ from the French Grains; since, as, he observes, 688 Grains of the former sort, are Equiponderant but to 576 Grains of the later sort. And he subjoins, that, whilst he was writing these things, there was found by the more exact weights of the Mint, an Error in the former Estimate, of at lest half a Grain in 36 Grains. And elsewhere he gives notice, that, by two Relations, sent him from Rome, about the Number of Grains, Mersennus in the Paper entitled, Parisiensia Pondera, Corollar. 1. and 2. contained in a Roman Ounce, it appeared, that even that Number varied, since One of those Relations reckoned 612 Grains in an Ounce, whereas the other allowed it but 576 Grains. And yet this I do not wonder at, because I have myself found it so difficult in Practice, to get and keep Weights (for, as little as this is want to be suspected, the the very Air may, in time, a little altar them,) as exact, as I desired, that I left of the hopes of it. And one Remark, tho' commonly overlooked, I think too considerable to be here omitted. For, In the Paper called Galic. Nummis. whereas the accurate Ghetaldus' Tables of the Weight of Metals, and some few other Bodies, in reference to one another, are looked upon as the most Authentic that have been published & are accordingly made the most use of: 'Tis certain, that the Weights he employed are not divided, as Ours are. For, tho' indeed according to him, as well as with us, the Ounce consists of Four and twenty Scruples; yet the Scruple, which with us is divided but into 20 Grains, he divides into 24. But to return to Mersennus, a while after he had told us of the Difference between his repeated Trials, and Those of other Men, in determining the Weight of a certain Body, he has this Passage; which shows, that he was not over-confident of the Preciseness of all his own Determinations. Cum autem (saith he) pag. 37. lib. 16. Dixi, Chelin●m, undecim dici denariorum, credunt tamen alii decem dunt axat, nil assero. Having gone through the First part of my Answer, to the Second Query above proposed, it remains, that I proceed to the Other part; which perhaps will not need more than the following Reflection. I consider than, that tho' it be granted, that Hydrostatical Experiments are not always either singly accurate, or exactly agreeable among themselves; yet they may well be, both accurate enough to be of very good Use, especially in Practice; and lesle remote from being quite accurate, than any other Ways that have been hitherto known to be Practised, of determining the Proportions of Bodies in point of Weight and Bulk, and of measuring the Solid Contents of stable Bodies, whether heavier in Specie than Water, or lighter. The First part of this Reflection may be deduced, as a Corollary from, or at lest confirmed by, the greatest part of the foregoing Essay. And indeed, as little Skill as I have in hydrostatics, I would not be debarred from the Use of them, for a considerable Sum of Money; it having already done me acceptable Service, and on far more occasions, than I myself at first expected; especially in the Examen of Metals and Mineral Bodies, and of several Chemical Productions. And I have been able more than once or twice, to undeceive Artists and other Experimenters, that, bona fide, believed they had made, or were Possessors of, Luna fixa, (as they call it) and other valuable things: And to make a good Judgement of the Genuineness or Falsity, and the Degrees of Worth, or Strength, in their kind, of divers richer or poorer Metalline Mixtures, and other Bodies, (some Solid, and some Liquid,) whose fair Appearances might otherwise have much puzzled, if not deceived, me. But of This more may be found in another Paper. For I must hasten to the Second part of our designed Reflection, by representing, That our Hydrostatical Methods of discovering the Weights and Bulks of Bodies, tho' they be not Mathematically accurate, yet they are lesle remote from being so, than any Way of Mensuration of Bodies, (especially such little Ones, as we usually have need to examine on the account of the Materia Medica,) by the Geometrical Instruments, that are hitherto known to be Practised; or, by the Way, Verulam in Historiâ densi & rari, p. m. 8. etc. whereby the Tabula Coitionis & Expansionis Materiae per Spatia in Tangibilibus, etc. was framed by the renowned Sir Francis Bacon; whose judicious Reflections upon the Rarity and Density of Bodies, such as their measures are delivered in that Table, do sufficiently manifest, as the Philosophical Genius of the Author, so the Utility that may be derived from even such Determinations of the Bulks and Weights of Bodies, as fall short enough of being accurate. I might here relate, that, to convince some curious Persons, how much hydrostatics may be made serviceable to as accurate Mensurations, as aught to be expected in Physical Experiments; I desired a Virtuoso, First, to put together two Lumps of Metal (viz. of Tin, and of Lead) in a certain Proportion, that he was to conceal from me, but to set down in Writing to prevent Mistakes. Than I desired him to melt the Metals (whose respective Specific Gravities I knew before) into one Mass, and give me that Mass. And Thirdly, I weighed it carefully in Water; and did also Algebraically examine it. Which being done, I told him, that the Led, he had employed, amounted to such a Weight, and the Tin to such another; which being compared with the Quantities he had committed to Paper, the Difference was found to be little more than one Grain, and this itself probably proceeded from some scarce avoidable Imperfection in the melting, pouring out, etc. of the given Bodies. But because specious Arithmetic was employed in this Work, (to which, yet it was not absolutely necessary,) I shall lay no Stress upon it; because, if I mistake not, the past Discourse may suffice to give the Hydrostatical Ways, of Mensuration of Bodies, a preference to their Competitors; and may keep it from being presumptuous, to say, that they may be received as the best for Practice, till some other more accurate, and yet as firmly grounded, and as Practicable, Ways of accomplishing the same purposes, shall be proposed. FINIS. A Previous Hydrostatical Way OF Estimating OARS. Advertisements. I Know there is a greater Number of different kinds of Fossiles, than Those that are yet known to belong to the Materia Medica. And, I confess, that the Persons, which the following Paper is chief designed to assist, are those that explore Minerals with an Aim not at Health, but at Profit. But yet I was content, that the ensuing Discourse should accompany the foregoing Essay, as a kind of Appendix to it, because many of the Subjects, about which both Tracts are conversant, are the same; and the Fundamental Observation, (viz. about the Specific Gravity of Crystal or Marble,) and the Hydrostatical Way of applying it, in Explorations, is the same in both: and also, (and indeed, chief,) because I was made to believe, that it might, especially at this Season, be grateful, and not unuseful, to divers Searchers after profitable Minerals. This Paper (as the Inscription intimates,) was designed to be sent to the Learned Secretary of the Royal Society; when it was expected, that he would begin again to publish Monthly the Philosophical Transactions, that had been long suspended, and as long desired by the Curious. But since some Accidents have occurred, that occasion a further delay of their Publication, it was not thought fit, this Paper (after having been long already) should be any longer confined to my Closet. 'Tis true, that this Discourse, containing but an Application of an Hydrostatical Experiment; I am far, as I aught to be, from proposing it as a Treatise of the Docimastical Art; whose grand Instrument is, the Fire Skilfully managed. For which reason I have foreborn to set down in this Paper, any of the Flux Powders, or other Ways of Examining Oars, or of Reducing Them, or other Fossiles, to Metals or Regulus'; that either Say-Masters are want to employ, or I have devised, or tried, upon Minerals. But, this notwithstanding, our unpractised Way of Estimating Oars, may not be useless; and for that reason, will not perhaps be unwelcome to some, that Love Mineralogy, much better than they Understand it: Especially coming forth at a time, when many industrious Persons of this Nation are excited to look after profitable Minerals, by the Repeal (that has been made, since our Appendix was written,) of a discouraging Act of Parliament, made in the Reign of Henry the iv And tho' our Hydrostatical Way, of Estimating Fossiles, will not determine how Rich or Poor they are in this or that particular Metal; yet, (as is intimated at the beginning in the ensuing Paper,) it it may, on many occasions, serve to k●ep those that are Venturous, and not Skilful, from being deluded by Cheats, or from deluding themselves with ill-grounded Expectations; which the Promising appearances of divers Fossiles, especially Marchasites, will temptingly Invite, but never Answer. A Previous Hydrostatical Way OF Estimating OARS. Addressed to the Secretary of the R. S. SECT. I. Sir, AT a time, wherein so many ingenious, or industrious, A Way proposed for the previous Examen of Oars. Men appear very Solicitous to discover and to work Ours, both Here and in New England, and Others of his Majesty's American Colonies; it will not, probably, be thought unseasonable, nor prove unwelcome to the Seekers of Subterraneal Treasures, if my desire to do them a piece of Service, make me borrow of a Paper, I long since wrote about some things relating to the Materia Medica, a few Paragraphs, that contain a Way of Exploration of Minerals; which tho' it reaches but to One of their Qualities, will, perhaps, by reason, of the Considerableness of of This, keep, on certain Occasions, some Searchers after Ours from beginning chargeable Works, or prosecuting them with too great Expectations, which are usually followed by proportionable Disappointments. And I make the lesle Scruple to suffer this Fragment to leave its Company, and present itself to you; because, after the misfortune, I have formerly signified to you, of the Loss and Spoiling of several of my Writings, I know not when, if ever, I may have Opportunity of Communicating to my Friends the Treatise, that these Paragraphs belong to. That Part of the forementioned Treatise, that concerns my present purpose, is founded on an Experiment, whereof what you are about to read, is One of the Applications. I shall than succinctly inform you, that the Observation, whereon my Discourse was grounded, is double, as will by and by appear; and that the Rise of it, which will help to understand the Nature and Influences of it, was this. I thought fit, (for Reasons elsewhere given) to found out, what was the Specific Gravity of a pure Stone, such as I supposed Crystal or White Marble, or a Stony Icicle, to be; and found it by the Hydrostatical Way of Trial, (doubtless not unknown to You,) that is delivered in the Essay called Medicina Hydrostatica, whereof when you please, you may command a sight, to have to clear common Water, equal to it in Bulk, or Magnitude, pretty near the Ratio, or Proportion of two and an half to one; or, which is somewhat more obvious to conceive, as five to two. I said, pretty near, because 'tis not always exact, nor need be for our present purpose, but usually enough does somewhat rather exceed that Proportion than fall short of it; but that is so little, that it may, on all common Occasions, be safely enough neglected by a Mineralist: Thou, if one pleases, one may make use of the Proportion of 2 ¾ to 1, that is, of 11 to 4. SECT. II. THe Uses, that may be made to our present purpose of this Fundamental Observation, are either of a more General, or of a more Particular, Nature. As to the first of these; When my Intention is only to discover in general, Whether a Fossile propounded, or perhaps casually lighted on, may with probability be judged to contain any Substance, either Metalline, or belonging to some Fossile of Affinity to a Metalline Nature; and also, Whether, in case the first Question be resolved in the Affirmative, the proposed Body does, indefinitely speaking, contain much, or but little, of the Metalline or other Adventitious Substance: When, I say, I would only make those General Inquiries, I weigh the Body I would examine, first in Air, and than in Water, and observe the Proportion in Specific Gravity between them; and if I found it weigh either lesle, or but little more, than Crystal or Marble of the same Bulk, I judge it unlikely to contain any Metalline Portion, considerable for its Quantity. And if it weigh manifestly, or somewhat considerably, more than Marble or Crystal, I guests, that, in Proportion to that Excess, it abounds, more or lesle, with a Metalline Ingredient, or one or other of Affinity to a Metalline Nature. To explain myself a little by two or three Examples; 'tis known, that the Magnet is vulgarly reckoned amongst Stones, and its great Hardness confirms Men in that Opinion. But having observed, that Lodestones, especially those that come from some Places, that I elsewhere take notice of, seem to be apparently more ponderous than common Stones of the like Bulk; We weighed them in Air and Water, and found their Specific Gravity, especially of some of them, The Author means a Paper containing Experiments and Observations about the Loadstone, as 'tis a Mineral. so far to exceed That of Crystal or Marble, that it could not be difficult for us to conclude, that these Fossiles contained a not inconsiderable Proportion of Metalline Matter, which, by Collateral Experiments, delivered in another Paper, appeared to be of a Martial or Ferruginous Nature. Emeri is a Fossile well known to many Tradesmen, especially Armourers, & Gunsmiths, by whom 'tis commonly reputed a mere Stone. But finding that its Weight in Water considerably exceeded That of Crystal of the same Bulk, since it was to that Liquor very near, as 4 to 1; I conjectured, that it contained a Metalline Substance, as afterwards, by proper Trials, I found it to do. Upon the same ground, (its Weight in my hand) I concluded, that Lapis Haematites, that is commonly sold in Shops, and, as its Name witnesseth, passes for a Stone, did not sparingly participate of a Metalline Ingredient; in prosecution of which Conjecture, I quickly thought on Ways whereby I discovered, that Iron or Steel was the Metal it contained. And not to accumulate Instances in this place, I shall advertise you in general, (what perhaps may hereafter be found useful to several Enquirers) that, upon the Grounds hitherto mentioned, I was invited to guests, that divers Bodies, that were little suspected to be of a Metalline, or Mineral, Nature, did really contain a Portion of Substance that was so. And, I remember, in particular, that, having met with Granats of several sizes, that were not Bohemian, but were found in other Parts of Europe, and some that I discovered in a kind of Talc, that was brought me from America; which Angularly figured Stones, I suspected by their Weight to be Metallic, and found, by hydrostatics, to have a Specific Gravity considerably surpassing That of Crystal. Upon these Grounds, I say, I supposed them to participate, and that not very sparingly, of a Metal, one or more; and, by other Ways of exploring, found, that I had guessed aright; since I was able, notwithstanding the great Compactness of such seemingly vitreous Bodies, to discover there a Decomposition, and extract thence a Metallic Substance. To these I might add other Fossiles, and some that were not, even by Men not unskilful, suspected to have any Metalline Ingredients. But I have not time to speak of Them, and therefore shall proceed in the lately begun Discourse. SECT. III. TO illustrate than the general Observation, formerly laid down, and make it more distinct, I shall subjoin the following Remarks. First, I do not pretend, by this Way, to make any more than probable Conjectures and Estimates, about the Contents of the Bodies, I examine by it: But tho' the Estimates, grounded on it, be not always True, yet they may be frequently Useful, as may be gathered from some of the subsequent Observations. Secondly, If the Fossile proposed be lighter, especially if it be much lighter, than so much Crystal, it is an almost certain Token, that it is not a Metalline Ore. And this Negative use, if I may so call it, of our Hydrostaticks, may be more safely relied on, than the Affirmative Consequences usually can be. Thus, when I found that Jet, tho' a Fossile dug up in Veins, especially in the Pyrenean Mountains, (as a Learned Man, whose Brother has there a Mine of Jet, assured me) has far lesle of Specific Gravity, than Crystal, I conclude it to be no Metalline Body. The like Inference I make, on the same ground, as to Fossile Amber or Succinum, Sulphur vive, and the Observation holds in common Sulphur, (clear or Semidiaphanous) English Talc, Venetian Talc, and some other firm Concretions, whether Brittle or not, that are dug out of the Earth. Among these, I think fit to mention particularly Black-Lead, jest the Name it bears, should deceive Men into a Belief, that 'tis an Ore of that Metal. For having found its Weight, in reference to Water, to be but as 1 86/100 to 1. And, gathering from the Smallness of its Specific Gravity, that it would prove to be very unlike our true common Lead Oars, I found, upon Trial purposely made, that, 'twas a Mineral sui generis, and seemed, upon the score of more than one Quality, to be of kin to a sort of Talc, that I have met with. Thirdly, We should distinguish between the several Uses, that Fossiles may be sought for, and examined, by Men of different Professions, or Designs. And therefore, if a Fossile be found to be somewhat, and yet but very little, heavier in Specie, than Crystal or Marble; it may possibly have a Metalline or Mineral Portion, which, tho' very small in quantity, may consist of such Efficacious parts, as may make it deserve the Esteem of a Jeweller, a Physician, or a Chemist. But if the Surplus of Specific Gravity be inconsiderable, the Fossile itself will be so too to a Mineralist, that seeks not to gratify his Curiosity, or make a good Medicine, but to fill his Purse. For the Charge and Trouble of working a Fossile, so poor in Metalline Substance, will probably either exceed the Profit, or keep it from being considerable; whereas, if the Specific Gravity do much exceed That of Marble or Crystal, it may give good hopes of proving a Subject profitable to be wrought on. Fourthly, But, here I must give notice, that, tho' for the most part, the great Ponderosity of a Fossile proceeds from a Portion of some Metalline Substance, more strictly so called, that is embodied with the other part of the Concrete; yet this alone is indeed a certain Sign, that the Fossile is not a mere Stone, but is not alone a sure Sign, that the Mineral Portion is properly Metalline; and therefore, where there is just Cause of doubt, 'tis best to endeavour by some Collateral Signs to resolve it. The Reason, why I thought fit to give you this Admonition, is, that, besides Metalline Oars more properly so called, there are other Fossiles, which some call Semi-Metals, others Media Mineralia, and others again give other Appellations to; which Fossiles, tho' of Affinity to Metals, are want to be distinguished from true Metalline Oars; such (Fossiles) as are (that I may here name the principal of them) Antimony, Bismuth, (usually in our Shops called Tin-glass) Lapis Calaminaris, and Pyrites, commonly called Marcasites, and vulgarly, in English, Vitriol Stones.) But there will not perhaps occur many Cases, wherein it will be necessary to have recourse to Collateral Signs, to discern, Whether the Mineral Portion of a Fossile, be, in a stricter Sense, of a Metalline Nature, or not: For these Semi-Metals that I speak of, are most commonly found either in Veins, or in Masses, or great Lumps of their respective Kind's; and easily discover, to one that considers them with so much as a moderate measure of Attention and Skill, what Species of Fossiles they belong to. I have indeed from Devonshire received a Lump of Matter, which the Owner of the Mine, not knowing what to make of, desired my Opinion of, wherein I found some Antimony mixed with Lead, which was the Predominant Body. But such Mixtures occur not often enough, at lest here in England, to keep our Way of Estimating ponderous Fossiles from being, on most occasions, useful. SECT. iv FIfthly, 'Twill be almost necessary to give you notice in this place, that there may be a twofold Estimate made of the Specific Gravity of Oars; One, when the Metalline Body proposed is weighed in its natural State, that is, as 'tis taken out of the Earth, accompanied with the Sparr, or other Heterogeneous matter, that firmly adheres to it, (only the lose Earth being first washed of:) and the Other, after it has been beaten small and separated from stony, and other Heterogeneous, Substances, by the help of Water; where being skilfully agitated, there is easily discovered a notable Disparity in Weight between these, and the Genuine, or Metalline, parts of the Ore, which being thus severed from the rest, are called, for instance, washed Tin, if afforded by a Vein of that Metal. And sometimes also 'tis very Useful, if not Necessary, to prepare the Ore by roasting it, (as they speak) once, or oftener, or by keeping it several hours in a competently strong Fire, as is usually enough done to prepare Copper-Ore, especially if it be stubborn. I have distinctly mentioned these Two States, wherein the Weight of an Ore may be estimated; because, I have observed, that in several Cases 'twill much import the Experimenter to distinguish them carefully. For several Oars, which, in their natural State, have too little of Specific Gravity, to make them judged worth the Charge of being wrought, may yet, being prepared by Water and Fire, afford a Metalline Portion so heavy in Specie, that it may give fair hopes of containing in it some Portion of Silver, or of Gold; and, in that case, a small Proportion of the Former, and a much smaller of the Later, would tender the Ore considerable, and make it pretty Rich; tho' not in reference to the quantity it yields of the predominant Metal, as Led, Tin, or Copper; yet in a more absolute Sense, as it may better recompense the Charges of him that shall work it. Which brings into my mind, that sometime ago a piece of Led Over, than brought out of Ireland, being offered me to judge of; I found it so light in the Lump, that I thought it not at all worthy to be wrought for Lead; but afterwards upon Trial it appeared to be, tho' very poor in that Metal, yet so well stored with Corpuscles of Silver, that I scrupled not to encourage the Owner to bestow Pains and Cost upon it. SECT. V BUt there is one Kind of Minerals, that I have observed to impose on Men so often, that I think it necessary to take a particular notice of them in this place. For, not to mention Examples, that I might draw out of the Books of Travellers and Navigators, I have met with I know not how many, that have built great hopes, and some, (which is worse) that have been at Charges upon those illusory Expectations of great matters from Marcasites. And, I remember, I have had sent me, or brought me, not only from Places nearer home, but from hotter and colder Countries of the Indieses themselves, Fossiles, whereof I was earnestly desired to give my Opinion, that I found to be but Marcasites: And many of these Fossiles having two Qualities, that make them very fit to delude the vulgar, and the unskilful, namely, first, a Multitude of shining streaks, or other glistering parts usually of a Colour near enough to That of Gold, and sometimes to That of Silver; and than, a Ponderousness usually not inferior, at lest, to that of true Metalline Oars; Marcasites, I say, being thus fitted to delude the unskilful, I have had much ado to undeceive some, that brought or sent me them from America, of the pleasing Confidence they had entertained, that these promising Fossiles were Lumps of rich Ore of Gold, or Silver. Wherhfore since their Ponderousness (which is the Criterion of Minerals, I am now treating of,) is One of the Two chief Things that delude so many, I think it expedient, to subjoin some few, but various, Instances of the Specific Gravity of Marcasites, whereby it may appear, that some of them are, Bulk for Bulk, far more ponderous than divers true Metalline Oars, that I have tried, have been found to be. And indeed this great Ponderosity has several times invited me, before I made any Artificial Trial of propounded Fossiles, and sometimes before I took them out of the Bags or Papers to look on them, to judge, tho' perhaps to the Surprise of those that brought them, that they were not true Oars, but Marcasites. And, because this Mistake is speciously grounded, and has deceived many, whereof some have undertaken Voyages betwixt Europe and the Indieses, upon confidence of the value of these glistering Stones; I shall decline a little the Method of this Paper, which confines me to the Hydrostatical Way of exploring Minerals, to advertise those whom it may concern, that they may easily try almost any Stone, that, by its great Weight and Lustre, they suspect to be a Marcasite, if they put it, either within a Crucible, or, without One, into a well-kindled Fire, and blow now and than upon it with a pair of Bellowss. For, by this means, the Sulphur, wherewith Marcasites are want to abound, (so that I remember, that even by Distillation in a close Vessel, I had ℥ iv of good Brimstone, like the vulgar, out of lb iij of the Stones) will take Fire, and burn with a Flame for the most part blue, like that of common Sulphur. And, if when it ceases to flame and smoke, you take it out of the Fire and let it cool, you will found it deprived of all the gaudy appearance of rich Metal it had before, and turned to a brittle blackish Substance, differing enough from That of a Metalline Ore, more strictly so called. These last words I add, because, in a lax Sense, 'tis easy to show, that Marcasites, at lest those that I have tried, may be looked upon as a kind of Metalline Bodies. For, besides that I have found divers of them to contain Particles of Copper, I found all, that I purposely examined, to contain, and some of them plentifully enough, Corpuscles of Iron or Steel, as plainly appeared, when, after the newly mentioned Calcination, (for with crude Marcasites I found not the following Trial to succeed) I applied to the pulverised Remains a vigorous Loadstone; to which great multitudes of Martial Corpuscles quickly adhered. And, I remember, I found in a Catalogue of the Fossiles of Misnia, published by the experienced Kentmannus, that, under the Head or Title of Pyrites, he brings in several Marcasites, whereof some contained Copper, others Silver, others Gold, and others both the last named Metals; which brings into my mind, that, having presented, among other English Minerals, a curiously shaped, and very fine Marcasite, to a Virtuoso, that is now Overseer of one of the Emperor's best Ours; He quickly examined it by a peculiar Way, not known to me, hoping to found in it some Gold or Silver; but, instead of that, obtained a Portion of running Mercury, which he was pleased to present me, and which, I presume, I may have yet by me. Thou I thought it needful to give the foregoing Caution about Marcasites, for the Reasons before expressed, yet my Design is, only to keep the lesle skilful from being deluded by their promising appearance. For otherwise I do not deny, but that 'tis possible for a skilful Artist, to make (at lest of some sorts) of them a gainful use; either by fixing the Volatile Gold or Silver, that may be found in some of them; or, by graduating Silver, by their means; or, perhaps by some other Ways, that I can but guests at. But (to add That on this occasion,) that, for which I much more value Marcasites, is, That (NB) somewhat more than bore Conjectures make me think, that, being dexterously handled, and perhaps even without Additions, they may afford very noble, as well as uncommon, Medicines; and particularly in Continual Fevers, tho' their Operation be usually scarce sensible, but by their good Effects. SECT. VI ON this occasion, I must not forbear to give an Advertisement, that may be of good Use to divers Examiner's of Oars, especially such, as are Novices in the Art of reducing them. And it is This, that, as to many, who make Trials of Oars, tho' they much value their own Flux-Powders, or Those that are cried up by others, yet they commonly act, as if they expected nothing from those that they prefer, but that they should more than Others facilitate the Fusion of the Oars; as that which being once done, the Metalline part will be separated by its own Weight, or, as it were, Spontaneously. But yet, having purposely examined the Matter more nicely, and compared the Quantities of Metal, that we obtained from two Portions of equal Weight of the same Ore, we found that those Proportions did very considerably differ, tho' that which yielded lest Metal was fluxed down with a Fondant (as the French compendiously call, what Our men, after the Germane, call a Flux-Powder,) that is dear enough, and not undeservedly esteemed, when such Oars are to be handled. And I little doubt, but that from other Metalline Oars, a greater Portion of pure Metal may be obtained by some, but little employed or known, Fondants, and perhaps cheap Ones too, than by Others that are much more in use and famous; Of which I may elsewhere give some Instances: Now, One that first occurs to my Memory, was afforded me, by two equally heavy Portions of the same Led Over devoid of Sparr; whereof One, being reduced with a due Weight of Nitre and Tartar fulminated together, afforded much lesle of Malleable Lead, than was obtained by means of half or a quarter of the Quantity of Filings of Mars, which, for Trials sake, I than employed on the Other; to show, how much better a Reductive of that kind of Ore, that Metalline Flux was, than even a sharp and fiery fixed Salt. And yet, (to give you an Instance in a much more precious Mineral than Led Over,) I shall add, that having, for Curiosities sake, tried some Ounces of good native Cinnabar finely pulverised; one half with a fixed Alcaly of Tartar, and the other with a different Flux-powder, we obtained from the first Parcel twice as much Mercury, as we did from the other half, destilled with another fixed Alcaly; even tho' it were of a Mineral Nature. Some Observations about Native Gold. SECT. VII. GOld, being by far the most Noble, and Precious, of Metals, About the Hydrostatical Examen of Gold and its Ore. it may be ill taken, if I should here leave the Ore or Mineral, that affords it altogether unmentioned; and therefore, tho' I have but Two, or Three, Observations pertinent to my present Subject, to offer about it, yet I think it may not be useless to say somewhat of that Ore in this place. I know, there are many learned Men, and even Chemists, that think, there are no such things as Gold Ours, properly so called. And, I confess, that I myself was long kept from being confident of the Affirmative. And I was induced to this Diffidence by considering, that tho' having had the Honour for divers Years to be a Member of his Majesty's Council for Foreign Plantations▪ I had the opportunity to converse with a considerable Number of Navigators, and other great Travellers, and with divers Persons, that had settled themselves in the Indieses, I made it more than once my business to inquire, not, Whether they knew of any Golden Ours in the popular sense of the word, for, I knew, that there are in Hungary, Macedonia, and some other Countries, Ours that afford Gold enough to deserve to be wrought for it: but▪ Whether there are any real Ours, or Veins, whereof Gold is manifestly the predominant Metal. Having, I say, proposed to many this Question, I was answered, That some of them indeed had heard of such Ours, but none of them had ever seen any. But afterwards I saw some Ore that I judged true, that was presented to his Majesty (Charles the Second; and I also received from an unknown Virtuoso, residing in the East Indies, together, with a very civil Letter (which I wished had been more Historical and lesle Complimental,) among other lesle valuable pieces of Ore, One in whose Clefts, and a little beyond them, there appear some Lumps, wherein by their Colour, and other Signs, 'tis so apparent, that Gold is the predominant Metal, that I little doubt, but that, if I would spoil the Lump by breaking the Spar, I should found these Metalline Protuberances Malleable, without the help of the Fire. But being unwilling to destroy the Entireness of it, I shall make only a few, and short, Remarks about this Ore. The biggest Piece, and that which was best furnished with Metalline parts, being about an Ounce and a quarter in Weight, contained so great a Proportion of Spar, in reference to the Metal, that its Weight to an equal Bulk of Water was but as 2 91/100 to 1. But somewhat to compensate this Smallness of the Metalline Portion; That, that was of it, seemed to be all Gold, there being no Sign of any other Metal in that Lump of Ore, nor in some lesser Ones that I received with it. The Spar (as our Mine-men use to call that stony Matter, in which the true Ore is immediately lodged,) did not look like the Spar of Lead Over, or that of any other of our English Metals that I have seen, but seemed at first view to be a kind of white Marble with a dash of Yellow. And upon Trial, I found it to differ more from the Spar of Lead Over, which, with us, is usually White, and and almost Semi-diaphanous than in the Colour. For, whereas our Spar of Lead Over is oftentimes so soft or tender, that it may easily enough be cut with a knife, we found the Sparry Portion of our Gold Over to be a Solid stone, and that so hard, that, being struck with a piece of Steel, it would yield Sparks of Fire. Whereas also I found, that the Spar of Lead Over would be easily enough, and in a short time, (as about a quarter of an hour) calcined to a kind of Lime; our Golden Spar, tho' kept some hours read hot in a Crucible, did not appear to be at all calcined. And whereas I had formerly observed, that I could easily dissolve the Spar of Lead Over in some Acid Menstruums and even in destilled Vinegar itself, I did not found, that our Golden Spar, tho' kept divers hours in stronger Menstruums, as Spirit of Salt, Aqua Fortis, and Aqua Regis, was dissolved or manifestly wrought upon by any of them; as if it were of a glassy Nature, as well as of a very hard One. A piece of Spar, that had scarce any Gold at all that could be discerned, being Hydrostatically examined, was in Specific Gravity to Water, as 2 65/100 to 1. which Ponderosity does but very little exceed That of white Marble, or That of some good Spar of Lead o'er that was compared with it. If I had received a greater Quantity of Gold Over, I should have given a lesle imperfect Account of this Subject. But these Notes, such as they are, may, perchance, not be unwelcome to some of those many English and other Searchers for Ours, that have never seen true Gold Over, or have not had Liberty to make any Trials upon it, and yet are in Search of Gold Ours, especially in Jamaica, where, if I much mis-remember not, the * General Venables. inquisitive Gentleman, that conquered it for the English, told me, at his return thence, that the Spanish Governor of the Island, when his Prisoner, confessed to him, That there was Mineral Gold, tho' the Spaniards did not dig deep for it for want of Workmen. SECT. VIII. BUt by the mention I have made of the true Ore of Gold, I would not discourage any from seeking for that rich Metal in the Veins of some other Metals; because, in divers of these, I know it may sometimes be found blended with predominant Minerals. This may appear by those Hungarian Copper Ours of Cremnitz, Memoirs for the Natural History of T●●. whence a considerable Quantity of Gold is yearly obtained. I have elsewhere also taken notice, that I have seen an English Tinore, Part of which I presented to the King, wherein there lay, in little Cells, a good number of small Leaves or Chips of Gold, which I saw there with pleasure. And tho' the Tin-men, not being able to separate them with Profit, usually melted both the Metals together, and sold the Product for mere Tin; yet an experienced Gentleman, who was Owner of the Mine, assured me, that One of his Workmen, who had many little Children, employed them with good Profit, to pick the Gold with their small Fingers out of the skilfully broken Ore. And tho' Lead-Mines be looked upon, as those, which the Matter, whereof Gold is made, is seldomest found to be near, and does as it were avoid; yet, there is a place in Scotland, (whose Name I remember not,) where, over a Led Mine, upon or near the Surface of the Ground, they oftentimes found Grains or bigger pieces of Native Gold without Spar; some of which by the ingenious Owners favour, I was Master of, and thought sometimes worthy of being presented to that curious Examiner of Oars, his Highness' Prince Rupert. And still I have one bit of Native Metal by me, which, if I much mistake not, I had from the same place: which Fossile, tho' I found it Hydrostatically (because being Native I would not melt it) not to be, as the Owner supposed, pure Gold; yet Gold is the predominant Metal in it, and the piece weighs forty odd Grains. Since I wrote the last foregoing Lines, I have, in an old Collection of my Notes, found Three; whereof the First is thus set down, A Grain of Scotch Gold, such as Nature had made it, without any adhering Stone or Spar, weighed ʒiij + 21 Grains: The Second thus, Another Grain of the same Gold, that had here and there some little Stone or Spar sticking to it, and partly enclosed in it, weighed ʒiij + 3 Grains; So that the Heterogeneous Substance being, according to my Estimate, abated, it weighed about ʒiij: And the Third is subjoined in these Terms, A Grain of Scotch Gold weighed in Air, 43 Grains; in Water. 39 ½ Grains: Differ. 3● ½ Propor. 12 ●/● to 1. This Lightness of a Yellow Metal (heavier than Brass or Silver) deserves a Reflection; but I cannot stay to make it. It several times happens, that, among the lesser Grains of Gold, that are more properly called Sand-Gold, there are found pieces, some of which I have seen, that are singly big enough to be tied about with an Horsehair, and so weighed in Water, as Lumps of Ore of other Metals are want to be. And to such bigger Fragments of Gold, 'tis manifest, by what has been already delivered, that our Hydrostatical Way of exploring may be usefully applied. For since, according to the famous and diligent Mersennus, and some esteemed Writers, pure Gold is to Water of the same Bulk, as (about) 18 to 1; and by my Examen of very fine Gold, I found, that it equals about Nineteen times the Weight of as much Water, (I say, about, because I unhappily lost the exactest of my Trials upon Gold, among those made upon the other Metals in a most exquisite Balance) as is equal to it in Bulk; it will readily appear, Whether the Fragment proposed be perfectly pure or not. For, if its Weight amount to near Nineteen times as much Water in Quantity, we may conclude it to be unallayed; and, as it wants lesle or more of this Ponderosity, we may conclude it to be more or lesle pure. SECT. IX. 'TIs known, that, since we began effectually to cultivate the African Trade, it frequently brings into these Parts, besides things of lesle value, considerable Quantities of what, from the most usual Size of it, is by many called Sand-Gold; but which, by reason of the very unequal Bulks of the Grains, may perhaps justly be called Fragments of Gold; since being brought from the Maritime parts, where no Ours of Gold are yet found, they seem to have been broken of and washed away from hidden Veins by the violence of Waters, that, having carried them as far as they were able, left them a Prey to Men. Now, (because that unless it be perhaps brought by, or for, some Virtuoso) there is scarce any Gold that comes into Europe in Lumps, under the form of Ore; but a great deal that is brought from Guinea, (and those other parts of afric, which, for that reason, are comprised under the Name of the Golden Coast) in the Form chief of Sand or Gravel, grosser or smaller, and partly also of lesle minute Pieces; it may conduce to the scope of these Papers to take notice, that, in making Estimates of the Genuineness, and the degrees of Purity of these native Fragments of Gold, our Hydrostacal Way of exploring may be of no small use. For first, when we have once discovered the Proportion between pure or tightly refined Gold, and Water equal to it in Bulk; (which Proportion I have lately given exactly enough, for our present purpose,) 'tis easy, by our Hydrostatical Method, to examine the Fineness of any other Gold proposed; so, at lest, as to know, whether it be perfectly Fine; and if it be not, whether it do considerably fall short of perfect Fineness. But since of this I elsewhere treat, I think it more proper to observe in this place, that when once a Man has found the true Specific Gravity of a parcel of Sand-Gold, (smaller or courser,) whose Degree of Fineness he knows by Collateral Trials, or some other Means, (whatever they be) He may (as was formerly noted when I spoke of Metalline Oars,) take this Specific Gravity for a Standard, with relation to which, he may make his Estimates of the Fineness of other parcels of the like native Gold, that he is concerned to buy, or to examine. And, by this means, he may oftentimes prevent that chief Fraud of the Negroes, whereof several Traders to the Golden Coast are not a little apprehensive; as being in danger to be much damnified by it. For they complain, that, tho' the Blacks be otherwise, for the most part, but a dull sort of People; yet they have often made a shift to cheat the Traders, by clandestinely mixing, with the right Sand-Gold, Filings of Copper, or rather of Brass, whose Colour does so resemble that of Gold, that the Fraud is not easily discerned. And in the Account of a late Voyage, made by the French, to the Coast of afric, to Trade especially for Gold, 'tis acknowledged, that the Officers were egregiously cheated by the Blacks, who, instead of paying them for the Wares they brought, with Powder of true Gold, gave them Powder of Brass, or gilt Copper, which those that were not accustomed to make Trial of, are, as the Relater complains, such Wares, in a scarce evitable danger to be cheated: as these French men confess they were in one day to the worth of a thousand Crowns. But, in regard, that, as Trial has informed me, Brass is not quite half so heavy as fine Gold of the same Bulk; if there be any considerable Quantity of Filings of Brass with the Gold; This Mixture being put into such an Hydrostatical Bucket, or wide-mouthed Glass, as is mentioned in the Essay, will manifestly weigh lesle in Water, than if it were all Gold. And by comparing its Specific Gravity, with that formerly found, to the Grain-Gold pitched upon for a Standard; the greater or lesser Decrement of the suspected Gold, will help to make an Estimate of the Quantity of Brass, mingled with the natural Gold. SECT. X. BUt, tho' my present Undertaking do not oblige me to consider Sand-Gold, otherwise than Hydrostatically; and, tho' it highly concerns Merchants and Others, that deal in so rich a Commodity as Gold, and that is by so many studiously adulterated, to be furnished with nice and trusty Balances; yet, because divers Persons, especially Seamen, that trade to the Gold Coast and other parts, where Sand-Gold is to be met with, do, (perhaps too often) without being furnished with good Scales and sufficient skill to use them, venture upon buying such precious Wares; it will not be to departed from my general and main Design, which is to serve the Public; if I deviate a little from my Subject, and add to the Hydrostatical Way, lately proposed, of examining Sand-Gold, Two or Three Chemical ways to the same purpose. First, than, if he, that would purchase Sand-Gold, doubts, that there are Filings of Brass (or of Copper) mixed with it; in case he have Aqua Fortis at hand, he may quickly discover the Cheat, if there be any. For, 'tis known to Chemists, that Aqua Fortis will not work upon Gold, and therefore, if there be Filings of Brass mixed with it, the Operation of the Menstruum upon those, together with the Colour betwixt blue and green, it will thereby acquire, will discover the Deceit. But, because if Nature hath mingled much Silver with the Gold, the Proof by Aqua Fortis will require Skill, and may puzzle those that want it; I shall add, that good Spirit of Urine may be substituted in its stead. For, I elsewhere show, that 'twill readily work upon Filings of Copper or Brass in the Gold, and gain from them a fine blue Colour; and this being a Menstruum not corrosive, like the other, but harmless to most Bodies, and a good Medicine for human Bodies in several Diseases, (as the Jaundice, Pleurisies, some kind of Fevers, Coughs and Asthmas) may be fit to be carried about in Voyages, and to be preferred to Aqua Fortis. And, to make the Operation of this Liquor on Filings of Brass far more quick, than if the Solution be attempted an ordinary Way; I thought upon the following Expedient. I took Filings of Brass, (and the like may be done with those of Copper,) amounting to the Weight but of Eight or Ten Grains, or perhaps lesle; and having with my Finger spread them somewhat thin upon a small piece of white Paper, I moistened them throughly with good Spirit of fermented (or putrified) Urine, (which will not dissolve Gold) that, by this means, the Air might promote the dissolutive Action of the Menstruum; which, accordingly, it did so well, that, to the surprise of the Beholders, there appeared, in lesle than a quarter of an hour, and sometimes in a few minutes, a manifest, if not also a deep and pleasant, blue Colour upon the Paper, or on some of the Filings, (as both. Those that carry with them Spirit of Hartshorn, or such other Volatile Alcalys for Medicinal Uses, (as some modern Ship-Chirurgeons do;) may, for a need, employ That instead of Spirit of Urine. Nay, one may for the same purpose make use of Urine itself never destilled, if it be Stolen and Rank enough, (as it grows to be, sooner in hot Airs than in others:) Since having for Trials sake moistened with such Urine some Filings of Brass, thinly spread on a piece of Paper, there was a manifest Blewness produced in about a quarter of an hour. But I thought also of another Way, which I presumed would be better liked by most Traders, as more Commodious; because the Agent, being in a dry Form, cannot, like Spirituous Liquors, be spilt; and tho' it be more easily procured, may serve the turn almost as well. This Agent is common Sal Armoniac, of which, when I have occasion to use it, I reduce a greater quantity to Powder, than I guests the quantity of Water, I shall need, will dissolve; that the Liquor may be satiated with the Salt. With this Brine I throughly wet Filings of Brass, (or Copper) after the forementioned manner, thinly spreading them with my Finger on a piece of Paper, or some other fit and flat Body; and in a short time (as about a quarter of an hour or lesle,) there will appear a Greenish blue Colour, drawn from the Brass by the Liquor: Which (Liquor,) I suppose, I need not tell you, will not work on the Gold, wherewith the Brass is mingled. SECT. XI. I Have observed such a Variety of appearances, and disguises, of Metalline Bodies, and some other Minerals, that I would advice those that are given to the Search of Ours, and other Fossiles to have their Eyes always open, when they pass (especially by Land) from one place to another; that they may be ready to take notice of any unknown, or uncommon, Fossile, that they chance to see in their Way; and that having taken it up, they do not neglect to pond it in their hands (which after a little Practice 'twill not be difficult to do, tho' not exactly, yet not unusefully) and, if they judge it to exceed the Weight of Crystal, or Marble, to examine it Hydrostatically at their first Conveniency. For there are in England, as well as in divers other Countries, useful Fossiles, that are want to be overlooked by the unskilful▪ and I have found in this Kingdom, even upon, or very near, the Highways, Eagle-stones; and some other Minerals, that were not suspected to be of English growth. And, I remember, that having occasion in the Country, to pass by the Workhouse of an ingenious Potter, that I sometimes employed in his Profession; and having viewed the ground somewhat attentively, among some other uncommon Fossiles that I took notice of, I made a discovery of Manganese, or Magnesia, whereof I gave the Potter an Advertisement, which he afterwards thankfully made use of, having found the Mineral very proper for the glazing and and colouring of his Vessels. Nor was this the only kindness, that skill in Mineralogy, as little as mine was, enabled me than to do him. For he having invited me to view, very privately, a place wherein there was great store of a Fossile Substance, that Men knew not what to make of, because they had not seen, nor heard of, the like in England: The knowledge I had of some Italian Ours, made me quickly guests, What it was that was taken for an unknown Metal. For 'tis true, that this Mineral was not divided into Lumps of such Shapes and Bignesses, as make glittering Fossiles pass for Stones among the unskilful, such as are the Marchasites whereof they make Vitriol, and are found by the Seashore, in or near the Isle of Wight, and, (tho' not so plentifullly) in other parts of England (where I have found them;) but ran a great way (and I had not Time or Liberty to try How far) under ground, like a Vein of Metalline Ore. But this notwithstanding, I judged the Mineral to be but a Marchasite, in a Form, unusual indeed in England, but which is not without resemblers in some parts of Italy; which Conjecture I found true the same day, by some easy Trials, that manifested it to abound much more in Vitriolate Salt, than any Marchasite that I had examined in the form of Stones. So that, tho' I had no opportunity to try, whether or not it contained any better Metal than Iron; yet I concluded, that, Caeteris paribus, it might be employed to to make store of Vitriol, in far lesle time, and with far lesle cost, than the Marchasites made use use of, in the Vitriol Works at Deptford, or elsewhere in England. I remember also, that a Mineral of an odd, tho' pretty, appearance, being sent me, whose Species was unknown to the Mine-men that dug it up, I guessed that it was a Fossile, that I had not found in a good Printed Catalogue of our English Minerals, (namely) the Ore of Bismuth. And in this Conjecture some Trials, purposely made of that Mineral, sufficiently confirmed me; and gave me cause to be sorry, that the Vein, that afforded it, was so very small, as the Diggers found it, of an Ore, that has Properties Curious enough; and is by some famous Chemists affirmed to have some that are, not only Rare, but Wondered. But the chief thing that invites me to recommend, in this place, to those that Travel, an heedful eye on the Ore-like, or ponderous Substances, that may occur to them, is, That One of the Applications of our general Remark, about the Specific Gravity of Fossiles, may be extended to an Use, that has not, that I know of, been made by Mineralists, and and which yet I thought fit not to overlook: because I see no need, we should be confined to examine only those Fossiles, whereof we can obtain Parcels, big enough to be weighed in Water in the entire Body. For besides other Minerals, that may be found profitable to the Physician, the Drugster, or the Mineralist; the Oars, or Wombs, of Metals themselves, may be divers times found disguised in the Form of Earth, or of Mud, easy to be dried: Which Fossiles, tho' (because they chance not be found in Lumps) unfit to be kept immediately suspended by an Horsehair; may be conveniently enough examined by the help of a Glass-Jar, whose Weights in Air, and Water, and their Difference, (which gives the Specific Weight of the Vessel) have been taken once for all, which I usually call an Hydrostatical Bucket. For this Vessel, being almost filled with the propounded Fossile, and carefully counterpoized in the Air, and than thoroughly wetted with Water; and when 'tis so, warily let down into the Water, and kept suspended by an Horsehair to a tender Balance; when, these things, I say, are done, the Difference between the Weight of the Mineral and Vessel, when they are under Water, and their former Weight, being observed; and the Specific Weight already found of the Vessel itself in Water, being substracted from that Difference; there will remain the Weight of the Fossile only, (which we here suppose, to be heavier in Specie than Water, and not to be dissoluble in it) or the Mineral itself, in that Liquor; and consequently, the Proportion between that Body, and Water of the same Bulk, as is elsewhere sufficiently declared. SECT. XII. TO manifest, that This Expedient may be of use in divers Cases, I shall only here observe, that a late Author, who hath published an Account of Swedland, declares, that one of the best sorts of Swedish Iron (which, you know, is much esteemed in its kind) is divers times found, in the Form of a read Mud, at the bottom of Lakes, or far lesser Stagnant Waters: which I the more readily believe, because I have found some English Okers (that pass but for read Earth, or Stone of that Colour;) to be richer in Iron, than I found some famous Oars of that Metal to be. And another experienced Writer, who gives us an Account of the Gold and Silver Ours of America, among which he spent several Years, takes notice, that Gold itself is found, from time to time, disguised into a reddish Earth, or is (tho' unsuspectedly) harboured in it. Vannochio. An Italian Mineralist, of repute in the last Age, doth also take notice, that a reddish sort of Earth doth sometimes contain a Portion of the richest Metals. I have observed some European Diamonds, as many call a sort of clear and finely-Figured Crystals, to grow in a read Earth; whence I have taken up pretty store of them. And an inquisitive Traveller, who has been in the Indieses, presented me with a certain Earth, which he affirmed to be from the Diamond Ours, (I presume, in the Kingdom of Colchonda) which I found to be also read, and which I made some Trials of, that belong not to this place. SECT. XIII. BUt the profitablest Use, that a Mineralists may make of our Hydrostatical Bucket, is, to employ it much in weighing Variety of coloured Sands, and Gravels; particularly, some hereafter to bementioned. And to let you see, by an easy Instance, how apt we are to overlook Sands for want of trying them by Weight, I shall not tell you, that I have sometimes seen a sort of Sand that was slighted as common or worthless, which, being washed and viewed in a Microscope, tho' none of the best, looked like an Aggregrate of small Granats, and perhaps was so; but shall here content myself to instance in that black Sand, that is commonly used in London and elsewhere, only to dry up the Ink of Words that have been newly written. For having observed when I had some quantity of this in my hand, that it was manifestly heavier than common Sand; I thought it worth the being examined by the Hydrostatical Bucket; by which Trial, that which we employed, appeared to be to Water of the same Bulk, near about as 4 6/10 to 1. And having, for Reasons that I cannot stay to mention, judged this Sand to be a Mineral of a Martial Nature, I was confirmed in my Conjecture, by melting it down with two or three parts of Antimony, and casting it into an Iron Cone. But I was more than confirmed in the same Conjecture, when, having tried it with a vigorous Loadstone, I found it to be far richer in Metal, than any of the English Iron Oars I had made Trial of, and (except perhaps One) than any of the Outlandish: For, having taken, at adventures, some Drams out of a much larger Quantity, and weighed it; I found, that at lest Seven parts of Eight would easily be taken up by the Magnet. But such Observations as these, are not the things that chief move me to recommend the Examen of Sands and Gravels to the Mineralist; particularly, those sorts of them, that, being somewhat ponderous, are Reddish or Yellow, especially if they retain those Colours, after they have been made read hot, and quenched in cold Water. Therefore to proceed to the mention of richer Sands, 'tis known, That, from the Coast of Guyny, European Traders, of several Nations, do yearly bring Gold, to a great value, which is washed or picked out of the Sand. And even in Europe there are Rivers, whose Sand is enriched by Grains of Gold, for which the Tagus that runs by Lisbon, and Pactolus, were famous among the Ancients. I knew an industrious Chemist, who owned to me, that he got Gold with Profit, from the Sand, which he found in some places of the Banks of the Rhine: and there is a little River in Savoy proceeding from the Mountains there, on whose Banks, after a Land Flood, I saw poor People busy themselves in seeking for Grains of Gold. Some Trial, (also) that I caused purposely to be made, confirmed me in a Conjecture, which possibly may hereafter prove Beneficial to many; namely, that the Sands of divers places, if they be Skilfully treated by a dextrous Chemist, may afford much more Gold, than is picked or washed, out of them in Form of Grains. For besides, that there may be many Atoms, or Corpuscles, of Gold that are so very minute, and stick so close to Grains of Sand, that they are neither taken notice of by the Eye, nor separable by washing, and picking; besides this, I say, there may, as I conceive, be many Particles of Gold incorporated with the Body of the Sand, which may be a Kind of Womb for matter of a Golden Nature, that a skilful Artist, by the help of proper Additaments, may separate with Profit especially, if, with lethargy or Minium, he first reduce the Sand to a Glass, and than take care to get the Volatile Gold, by giving it a pure Body fit to retain and fix it, such as is fine Silver: Out of which, I remember, we separated by Quartation, (tho' without Profit, because of the Charges, and of the small Quantity we could work with at once,) from as much vitrified Sand, and two or three fluxing Additaments of small price, as were contained in one Crucible, (that broke too, before Operation was near done,) sixteen Grains of pure Gold; that you may yet see, if you desire it. SECT. XIV. IT need not startle you, that, in reciting this Experiment, I made mention of Volatile Gold. For, tho', I know, that divers learned Men, and some able Chemists themselves, look upon it as a Fictitious thing; and that seems to bear a kind of Contradiction in its very Name; in regard of the perfect Fixity they presume to be an Essential property of Gold: yet I do not scruple to descent from them, being warranted so to do by my own Experience. For, I have, more than once, made use of a Way, wherein, by the help of an Additament, inconsiderable as to Bulk, and lesle as to Weight; one may, without a naked Fire, and in a Glass retort, sublime Gold, (not prepared by previous Calcination) sometimes in the Form of a yellow, or golden coloured, Salt; and sometimes, when the Operation succeeded better, in the Form of thin Crystals prettily shaped, Glossy, and as read as Rubies. But this upon the by; it may perhaps be more useful to Searchers of rich Fossiles not found in Lumps, if I take this occasion to observe, that when they meet with Sands, Earth's, Mineral Fragments, etc. that considerably exceed Crystal in Specific Gravity; and by the Place wherein they are found, or by other Tokens, give hopes of their containing Corpuscles of a golden Nature: When this, I say, happens, it will not be adviseable, hastily to reject such Bodies; but rather carefully to try, Whether they do not deserve a better Usage. For, having sometimes had the opportunity to discover Corpuscles of Mars, as Chemists call Iron and Steel, in a far greater Variety of Fossiles, and of Disguises, than even many noted Chemists would have imagined, or some of them could, upon heedful Trial, discover; I was much confirmed in my Suspicion, That Corpuscles of a Golden Nature may be concealed in divers Bodies, which are thought not to contain any Metal; and that in more of those Minerals, that are looked upon as Oars of some other Metal, because of its being manifestly Predominant, there may be mingled pretty store of Particles of Gold or Silver; which (because of the greater Quantity of that other Metal, or Mineral, that doth, as it were cover or disguise them;) lie unperceived, & usually unsuspected, by Persons not very well acquainted with such Matters; and yet may, by One that is very skilful, be separated even with Profit. SECT. XIII. BUt the Grounds of the forementioned Suspicion being as yet but Conjectural, I shall decline the particular mention of them in this place; and shall rather Advice, with reference to Oars in General, that those that would apply the hydrostatics to Them, do labour to procure Samples of the Oars of differing Ours, especially if they be found in the same Country; and do either by Trial or strict Enquiry inform themselves, what Proportion of the Metal, that denominates them, they contain. For these Portions of Oars and Minerals, being carefully weighed in Air and Water, and their Specific Gravities, being thereby made known, they may serve for a kind of Standard, by Comparison whereto we may oftentimes make not altogether unuseful Estimates of the Metalline Portions contained in other Parcels of Ore, of that Species, whether afforded by the same Mine, or Vein of it, or by any other of the same Metal) Hydrostatically examined. For Instance, our English Lead-Ores, that are worth taking notice of, may be, for distinction sake, divided into Three Kind's or Orders, and in each of these, there may be allowed a Latitude for greater, or lesser, Degrees of Goodness. The First sort is of those Oars, that, in the ordinary Way of melting, hold some of them from 30 lb of Lead, in an hundred Weight of Ore, to 40; and others to 45 lb of the same Metal, and these by several are slighted, as mean; and scarce, if at all, worth working; especially, those that hold under 35 or 40. As for the Second sort, that reaches from 45. to 60 lb, in the hundred; the most usual Proportion, I have found in many Trials hath been about half the Weight of the Ore in clean and Malleable Lead. These Oars are thought in, differently good and worth working: But other Oars comprised in this Second sort, held about 55, and some near 60, and these were looked upon, not only as Good, but pretty Rich. And for the Third Sort, it consists of those that yield from 60 to 80. in the hundred, and these Oars are justly reputed very Rich, (in lead) especially these that come any thing near 80; for, I confess, I never met with any that reached so far, but was assured by an ingenious & skilful Gentleman, Master of his Majesty's Royal Mint, that he had found some such upon Trial. But for me, I think that I have not above twice or thrice met with any that yielded me above 75. These looked exceedingly Promising, as if they were all Metal, and I observed, whether the thing were casual or not, some Lumps to be composed of divers great Cubes like Dices, sticking very hard to one another. The Considerations, that moved me to offer the Advice given at the beginning of this Section, invited me to make Researches of the Specific Gravity, not only of divers English Oars, as of Lead, Tin, etc. Of which I had carefully made a Collection, (that was lost by a sudden Fire, broke out in the place where I kept them,) but of the Oars that were presented me from several Countries, both in Europe and America; as Swedish Copper and Iron Oars, Germane Silver and Tin-Glass Oars; Hungarian Antimonial Oars; New English Lead, Iron, and Copper Oars, etc. The Effects of some few of which Researches, that chanced to come to hand, whilst I was seeking for some Hydrostatical Trials of Drugs, I thought it not amiss to insert in a Table annexed to the Medicina Hydrostatica; because perhaps they may be of some use, in making a previous Conjecture, about a Ours being, or not being, likely to be wrought with Profit, all other things concurring, that should do so. Which last Clause I desire should be taken notice of; because there are divers other Circumstances, besides the Proportion of the Metalline part in the Fossile, that are fit to be considered, [as, the Plenty, or Scarcity, of the Mineral; the Easiness or Difficulty of coming at it, because of its depth, or its being, or not being troubled with Waters, &c. its Nearness to Plenty of Fuel; and the Conveniency of Water to drive Mills; its Nearness to, or Remoteness from, the Sea, or some Navigable River, convenient for its Transportation, to omit other important Circumstances] before One gins to work a Mine; which as they hap to be Commodious, or Inconvenient, may tender the Attempt Adviseable, or Imprudent. But Sir, I perceive, (tho' late) that I have forgot, I was to writ, not a Book of the Trial of Oars, and other Minerals, but a moderately, sized Letter, about an Hydrostatical Way of Exploring their Specific Gravity. And therefore, to avoid increasing the already too great Prolixity of this Paper, by making an Apology for it, I shall lengthen it, only to beg you to Pardon it, and to look upon the Writer, as SIR, Your most humble and Obedient Servant R. B. Advertisement. TO give the Curious the Satisfaction of seeing at one view, and so of easily comparing together, the Specific Gravitys of a good Number and Variety of Bodies; and to save them the labour of turning over many Leaves of the foregoing Tract, to found the particular Body, whose Ponderosity they desire to know; I have caused to be annexed a Table, containing in an Alphabetical Order (tho' not a scrupulously exact One;) the Names of the Drugs, and other Bodies, whose Gravities are delivered in the foregoing Papers; without scrupling to add some others, that I chanced to light on, in turning over some of my old and forgotten Notes. But I must to the following Table premise this Advertisement, (warranted by several passages of the foregoing Papers here laid together) That 'tis not to be expected, Every one that shall try the Specific Gravities of the Bodies here mentioned, shall found all of them to be precisely the same, that the Table exhibits: Since, (not to mention, that perhaps every Experimenter will not employ so much Care, and be assisted with so much Use, in making Hydrostatical Trials, as Those this Table consists of were made with) the Difference, that may sometimes be found between his Trials and mine, may very probably be imputed to that Variety of Texture and Compactness, that may be found in several Bodies of the same kind, or Denomination; neither Nature, nor Art, being want to give all the Productions that bear the same Name, a Mathematical preciseness, either in Gravity or in other Qualities. The TABLE. A Weight In Air in Gr. In Water in Grains. Proportion. AMber 306 12 1 4/100 to 1. Agate 251 156 2 64/100 to 1. A piece of Allom-stone 280 ¾ 152 ¼ 2 1●/100 to 1. Antimony good and supposed to be Hungarian One 391 295 4 7/100 to 1. B Bezoar stone 187 61 1 48/100 to 1. A piece of the same 56 ½ 22 1 64/100 to 1. A fine Oriental one 172 60 1 53/100 to 1. Another 237 61 1 34/100 to 1. C Coral read 129 ¼ 80 ¼ 2 63/100 to 1. Crystal 256 140 2 21/100 to 1. Cornelian 148 103 3 29/100 to 1. Calculus humanus 2570 1080 1 72/100 to 1. Coco-shell 331 85 1 34/100 to 1. Native Crabs Eyes. 77 ½ 36 ½ 1 89/100 to 1. Crabs Eyes Artificial. 90 ½ 54 2 48/100 to 1. Calx of Led 138 ½ 123 8 94/100 to 1. Copper Stone 65 ½ 49 ½ 4 09/100 to 1. Common Cinnabar 802 702 8 1/●0 to 1. Cinnabar of Antimony 197 169 7 3/100 to 1. Cinnabar Native 197 171 7 57/100 to 1. Coral White 336 204 2 54/1002 to 1. Another piece fine 139 85 2 57/100 to 1. Calculus humanus 302 97 1 47/100 to 1. Copper o'er 1436 1090 4 15/100 to 1. Copper o'er Rich 413 314 4 17/100 to 1. Cinnabar Native, very sparkling 226 194 7 6/100 to 1. G. Gold Ore not Rich, brought from the East Indies 1100 682 2 63/100 to 1. Another Lump of the same 1151 717 2 6●/100 to 1. Granati Minera 217 147 3 1/10 to 1. Granate Bohemian 4 1●/100 to 1. H Haematites English 1574 1156 3 76/100 to 1. I Ivory 173 ½ 83 1 2●/100 to 1. L Lapis Manati 450 293 2 36/100 to 1. A Fragment of the same 218 ½ 123 2 29/100 to 1. Another 345 197 2 33/100 to 1. Another from Jamaica 2011 1127 2 27/100 to 1. Lapis Lazuli one piece 385 256 2 ●●/100 to 1. Led Over 686 590 7 14/100 to 1. Another Lapis Calaminaris 477 380 4 2●/100 to 1. Lapis Judaieus 261 2/1 164 2 ●●/100 to 1. M Marcasites 8●4 631 4 ●2/100 to 1. Another from Stalbridge 243 189 4 ½ to 1. Another more shining than ordinary 287 227 4 1●/100 to 1. Mercury revived from Ore Manganese a piece 321 230 3 ●●/100 to 1. Mineral Cornish like a shining Marcasite 145 129 9 6/100 to 1. O Osteocolla 195 108 2 ●●/100 to 1. Over Silver choice from Saxony 458 366 4 97/100 to 1. Another Piece 1120 960 7 to 1. Over Led from Cumberland Rich 1872 1586 ½ ●●/100 to 1. R Rhinoceros horn 8563 4260 1 99/100 to 1. Rock-Chrystal, another Piece 256 140 2 ●0/100 to 1. S Saphir Seed-Pearl Sulphur vive 371 185 2 to 1. German very fine 306 152 1 98/100 to 1. Slate Irish 779 467 2 49/100 to 1. T A Piece of Talc like Lapis Amianthus 596 334 2 31/100 to 1. Talc Venetian 802 508 2 7●/100 to 1. Talc Jamaican 1857 1238 3 to 1. New English Tin Ore, Mr. Hubert's 812 613 4 ●/100 to 1. Tin o'er black Rich 1293 984 4 11/100 to 1. Another piece Choice 2893 2314 5 to 1. Tutty a piece 104 83 5 to 1. Tin-glass 468 419 9 55/100 to 1. V Vitrum Antimonii per se 357 ½ 282 ½ 4 76/100 to 1. Vitriol Engl. a very fine piece 1093 512 1 88/100 to 1. unicorns horn a piece 407 195 1 91/100 to 1. POSTSCRIPT. WHen I began to sand the Essay, called, Medicina Hydrostatica, to the Press, and drew up the foregoing Preface to it, I intended it should in the same Book or Volume, be accompanied by another Help or two, to explore, and Improve the Materia Medica. But when the Essay itself, and the annexed Epistle about a previous Exploration of Oars had been Printed of; I could not but perceive, that the Bulk of those two Tracts so far exceeded what I expected, that if I subjoined what I at first designed to add to it, it would prove a misshapen Book, and inconvenient to be opened, wherefore it seemed expedient to divide the whole intended Work into two Volumes or Tomes, whereof what had already past the Press, should make the first, which that it might be the sooner serviceable should forthwith come abroad by itself, and the Second should consist partly of the other Papers abovementioned, as relating to the Materia Medica, and partly, of a Supplement to the first Tome, containing divers Historical Paralipomena, that by mistake were omitted, and are fit to be there supplied out of a fuller Copy, than that which by an Oversight was made use of at the Press. FINIS.