- Additional Information
- Notes on the Electronic Edition
- You are currently reading the normalized version of this text. Normalized transcriptions provide a tidied-up view of the original text. Editorial interventions are applied to expand abbreviations and correct textual mistakes. Additions are silently included within the body text and deleted text is not displayed. Switching to the diplomatic view of this text will not result in any changes to this document since it does not have any additions, deletions or editorial regularizations.
- Revision History
- 1 January 2001
- Catalogue information compiled by Rob Iliffe, Peter Spargo & John Young
- 1 August 2009
- Margarita Fernandez Chas tagged transcription
- 18 September 2009
- Yvonne Santacreu audited coding
- 29 September 2011
- Catalogue exported to teiHeader by Michael Hawkins
- 1 January 2001
- Download OTHE00086.xml and schema (advanced users only)
- Notes on the Electronic Edition
SIR ISAAC'S EARLY STUDY OF CHEMISTRY — AND OF ALCHEMY, AS SHEWN IN HIS LETTER TO MR. ASTON — HIS EXPERIMENTS ON THE METAL FOR REFLECTING TELESCOPES — HIS CHEMICAL PURSUITS BETWEEN 1683 AND 1687 — HIS RESEARCHES ON THE QUANTITIES AND DEGREES OF HEAT, WRITTEN AFTER HIS ILLNESS IN 1693 — HIS EXPERIMENTS ON THE RAREFACTION OF AIR, WATER, AND LINTSEED OIL — HIS PAPER ON THE NATURE OF ACIDS — THE RESULTS OF HIS CHEMICAL RESEARCHES, PUBLISHED AMONG HIS QUERIES IN HIS OPTICS — HIS OPINION ON FIRE AND FLAINE — ON ELECTIVE ATTRACTIONS — MANUSCRIPT WORKS ON ALCHEMY LEFT AMONG SIR ISAAC'S PAPERS — A BELIEF IN ALCHEMY PREVALENT IN NEWTON'S TIME — BOYLE, LOCKE, AND NEWTON STUDIED ALCHEMY AS A SCIENCE — OTHERS FOR FRAUDULENT PURPOSES.
ALTHOUGH Sir Isaac had directed his attention to chemistry at various periods of his life, yet his name has not been associated with any striking discovery in the science. I have therefore reserved an account of such of his chemical researches as have any real value, for the same chapter in which it is necessary to speak of his labours as an alchemist. It was doubtless during his residence with Mr. Clark, the apothecary at Grantham, that he first witnessed, and acquired a taste for, the practical operations of chemistry. In his earliest note-books there are copious extracts from Boyle and other chemical writers, and in 1669, when he wrote his interesting letter to Francis Aston, we see very distinctly the great interest he felt in chemistry, and the peculiar bent of his mind to a beliefin the doctrines of alchemy. He requests his young friend to observe the extraction of metals out of their ores, and the processes for refining them, and to notice as "the most luciferous, and many times lucriferous experiments in philosophy," "any transmutations out of their own species into another — of iron into copper, and any metal into quicksilver, or of one salt into another, or into an insipid body, &c." He returns to the same topic as he proceeds, and asks him to inquire if at the gold, copper, and iron mines at Schemnitz they change iron into copper by a particular process which he describes as done in Italy and other places. He refers also to a method used in various places in Germany of obtaining gold from its solution in the water and rivers by laying mercury in the stream, and straining the mercury through leather so as to leave the gold behind. He concludes this remarkable letter by asking his friend to inquire when in Holland about one Borry, who always went clothed in green, and who had escaped from prison, into which he had been thrown by the Pope, in order to "extort secrets of great worth both as to medicine and profit."
At the time when this letter was written, Newton was occupied with the construction of his reflecting telescope, and he was therefore led to institute new experiments on the alloys of metals, and the changes which they underwent by their union with other bodies. In his letter to Oldenburg in 1671-2, he has mentioned the general results of these experiments, which to a great extent have been the guide of all who have followed him in the construction of metallic specula for reflecting telescopes. He has left behind him, however, a full account of the composition of his specula, and of the method of founding them, in a paper carefully written in his own hand, and entitled De Metallo ad conficiendum speculum componendo et fundendo.
During the four years, from 1683 to 1687, the period in which the Principia was composed, he never abandoned his chemical experiments. Dr. H. Newton, w^ho was his amanuensis during that time, tells us that during six weeks in spring and autumn he was so constantly occupied in his laboratory that he was scarcely out of it either night or day — that the fire in it was almost always burning — that it was well furnished with chemical materials and apparatus, and that the transmuting of metals was his chief design.
At a later period, in 1692, he was engaged in chemical experiments, as appears from his correspondence with Locke; and at the very time at which Biot places the mental illness of Newton, I find a carefully drawn up record of chemical experiments made in that very month on the properties and action of barm, and on the distillation of the salts of metals. They were resumed in April 1695, and continued to February 1696, when he was called to London upon his appointment to the Wardenship of the Mint.
The only chemical paper of importance published by Sir Isaac, was read at the Royal Society on the 28th of May 1701, and printed in the Philosophical Transactions without his name, under the title of Scala graduumCaloris. The following are the principal points of the Scale: —
|Degrees of Heat.||Equal Parts of Heat.|
|0||0||Heat of the winter air when water begins to freeze.|
|1||12||The greatest heat at the surface of the human body, and that at which eggs are hatched.|
|2||24||Heat of melting wax.|
|3||48||The lowest heat at which equal parts of tin and bismuth melt.|
|4||96||The lowest heat at which lead melts.|
|5||192||The heat of a small coal fire not urged by bellows. The heat of a wood fire is from 200 to 210.|
In the original table eleven intermediate points of the scale are accurately determined, and the temperature of other parts of the scale less accurately indicated.
The first column of this table contains the degrees of heat in arithmetical progression; and the second contains the degrees of heat in geometrical progression, the second degree being twice as great as the first, and so on. It is obvious from this table, that the heat at which equal parts of tin and bismuth melt is four times greater than that of blood heat; the heat of melting lead eight times greater; and the heat of a small coal fire sixteen times greater.
This table was constructed by the help of a thermometer and of red-hot iron. By the former he measured all heats as far as that of melting tin; and by the latter he measured all the higher heats. The heat which heated iron loses in a given time is as the total heat of the iron; and, therefore, if the times of cooling are taken equal, the heats will be in a geometrical progression, and may therefore be easily found by a table of logarithms.
He found by a thermometer constructed with lintseed oil, that if the oil, when the thermometer was placed in melting snow, occupied a space of 10,000 parts, the same oil, rarefied with one degree of heat, or that of the humanbody, occupied a space of 10,256; in the heat of water beginning to boil, a space of 10,705; in the heat of water boiling violently, 10,725; in the heat of melted tin beginning to cool, and putting on the consistency of an amalgam, 11,516, and when the tin had become solid, 11,496. Hence the oil was rarefied in the ratio of 40 to 39 by the heat of the human body; of 15 to 14 by the heat of boiling water; of 15 to 13 in the heat of melting tin beginning to solidify; and of 23 to 20 in the same tin when solid. The rarefaction of air was, with the same heat, ten times greater than that of oil; and the rarefaction of oil fifteen times greater than that of spirit of wine. By making the heats of oil proportional to its rarefaction, and by calling the heat of the human body 12 parts, we obtain the heat of water beginning to boil, 33; of water boiling violently, 34; of melted tin beginning to solidify, 72; and of the same become solid, 70.
Sir Isaac then heated a sufficiently thick piece of iron till it was red-hot; and having fixed it in a cold place, where the wind blew uniformly, he put upon it particles of different metals and other fusible bodies, and noted the times of cooling, till all the particles having lost their fluidity grew cold, and the heat of the iron was equal to that of the human body. Then, by assuming that the excesses of the heats of the iron and of the solidified particles of metal, above the heat of the atmosphere, were in geometrical progression when the times were in arithmetical progression, all the heats were obtained. The iron was placed in a current of air, in order that the air heated by the iron might always be carried away by the wind, and that cold air might replace it with a uniform motion; for thus equal parts of the air were heated in equal times, and received a heat proportional to that of the iron. Butthe heats thus found had the same ratio to one another with the heats found by the thermometer; and hence he was right in assuming that the rarefactions of the oil were proportional to its heats.
In giving a notice of this paper, M. Biot justly observes, that it contains three important discoveries, one of which is the method of making thermometers comparable by determining the extreme terms of their graduation from the phenomena of constant temperature; the second is the determination of the law of cooling in solid bodies at moderate temperatures; and the third is the observation of the constancy of temperature in the phenomena of fusion and ebullition, — a constancy which has become one of the foundations of the theory of heat. This capital fact is established by numerous and varied experiments made not only upon compound bodies, and upon simple metals, but also upon various metallic alloys, which shows that Newton had felt the importance of it. "We may believe," M. Biot adds, "with great probability, that this work was one of those which he had finished before the fire in his laboratory."
This method of determining the date of important discoveries is certainly new in the history of science. Newton himself communicated this paper to the Royal Society in 1701, and, having no other evidence to guide us, we might have reasonably supposed that the experiments on which it was founded, and the important deductions which they authorized, were made a short time previous to its communication. M. Biot, however, follows a different rule. "The paper," he says, "contains three important discoveries, and therefore they must have been made previous to 1692-3, because, after the mental calamity which he believes befell him at that date, he was fit to write nothing but theology! Having already shown that, in every case in which he has thus reasoned, M. Biot has been incorrect in his decision, I was desirous of ascertaining the probable date of these experiments by an examination of Newton's note-books. In one of the oldest of these I found the following paragraphs written in a fresher ink, and in the handwriting of his later years: —
"The sealed thermometer, or another wholly like it, but made with oil, with the heat of my body, (to which I equal that of a bird hatching her eggs,) stands at the degree of . — March 10, . When water begins to freeze, it stands at the degree . . . .; when water begins to boil, at the degree . . . .; when water boils vehemently, at the degree . . . .; when water is as hot as the hand can endure to stay long in, at the degree . . . .; when tin begins to melt, at the degree . . . .; when wax begins to melt, at the degree . . . .; when molten tin sets, at the degree . . . .; when molten lead sets, at the degree . . . .; when melted wax sets, at the degree . . . .
"By dipping a bolt-head with a short neck into hot water, and holding it with its neck under water for six or eight minutes till the glass be as hot as the water — then stopping the glass with my finger, inverting it into a vessel of cold water, taking away my finger, letting it stand for an hour to cool; putting my hand into the cold water and stopping it again with my finger, when the . . . . water within and without the glass, taking it out and weighing the water drawn up into the glass, and the water which will fill the glass, and making allowance for in equal heats as 150 to 1.the ascent and descent of the barometer, I found how much the air was rarefied by the heat of the water; and by a barometer of lintseed oil, I found also how much the oil was rarefied by the same heat. The experiment I made twice, and found the first time that the rarefaction of air was to the rarefaction of water at equal heats as to 1 — the second time as to 1. 'Tis, therefore, in round numbers, as 10 to 1. By another way of reckoning, I found that the rarefaction of this oil was to the rarefaction of spirit of wine in equal heats, as 15 to 1, or thereabouts, for I did not measure this proportion accurately. From these the rarefaction of air was to that of
"The space which lintseed oil took up with such heat as I could give to a little bolt-head with my body, was to the space which it took up in such a degree of coldness as made water begin to freeze, as 41 to 40; and, therefore, the spaces which air took up in the same degrees of heat and cold, were as 50 to 40, or 5 to 4."
From this manuscript it is obvious that Newton was engaged in his experiments on the scale of heat at the very time that he was supposed incapable of such an effort; and as he had not then completed the inquiry, it follows that the discoveries which it contains were made at a later date. The historian of science has not a more painful duty to discharge than that of fixing the date of discoveries, but it is a duty which he is never called to perform unless there are conflicting claims submitted to his judgment. It is a singular obligation which a biographer imposes upon himself to fix the date of a discovery by the alleged insanity of its author.
The only other chemical paper of Sir Isaac's that has been published, is one of about two pages, entitled De Natura Acidorum. It is followed by other two pages, entitled Cogitationes Variœ, containing a number of brief opinions on chemical subjects, which have been more distinctly and fully reproduced in the Queries at the end of his Treatise on Optics. This paper must have been written subsequently to 1687, as it contains a reference to the Principia.
In the note-books and loose manuscripts of Sir Isaac, many chemical experiments and observations are recorded, but it is sometimes difficult to distinguish what is his own from what he has copied from other writers. As he seems to have considered his paper on the scale of heat the only one fit for publication, it is probable that he collected from his note-books the most important of the results at which he had arrived, and published them among the queries in his Optics.
The most interesting of these chemical queries relate to fire, flame, vapour, heat, and elective attractions, and as they were revised in 1716 and 1717, we may regard them as containing the most mature opinions of their author. He considers fire as a body heated so hot as to emit light copiously, red hot iron being nothing else than fire, and a burning coal red hot wood. In one of his note-books "he concludes that flame is nothing but exhalations set on fire, and that a burning coal and a burning flame differ only in rarity and density," that is, that flame consists of particles of carbon brought to a white heat, — an opinion of Sir Humphry Davy's. "Flame," he adds, "is nothing but a company of burning little coals dispersed about in the air, flame and vapour differing only as bodies red hot, and not red hot, by cold." He considers the "sun and fixed stars as great earths vehemently hot, whoseheat is conceived by the greatness of the bodies and the material action and reaction between them and the light which they emit, and whose parts are kept from burning away, not only by their fixity, but also by the vast weight and density of the atmospheres incumbent upon them, and very strongly compressing them, and condensing the vapours and exhalations which arise from them.
In his long query on elective attractions, he considers the small particles of bodies as acting upon one another at distances so minute as to escape observation. When salt of tartar deliquesces, he supposes that this arises from an attraction between the saline particles and the aqueous particles held in solution in the atmosphere, and to the same attraction he ascribes it that the water will not distil from the salt of tartar without great heat. For the same reason sulphuric acid attracts water powerfully, and parts with it with great difficulty. When this attractive force becomes very powerful, as in the union between sulphuric acid and water, so as to make the particles "coalesce with violence," and rush towards one another with an accelerated motion, heat is produced by the mixture of the two fluids. In like manner, he explains the production of flame from the mixture of cold fluids, — the action of fulminating powders, — the combination of iron filings with sulphur, — and all the other chemical phenomena of precipitation, combination, solution, and crystallization, and the mechanical phenomena of cohesion and capillary attraction. He ascribes hot springs, volcanoes, fire-damps, mineral coruscations, earthquakes, hot suffocating exhalations, hurricanes, lightning, thunder, fiery meteors, subterraneous explosions, land-slips, ebullitions of the sea, and water-spouts, to sulphureous steams abounding in the bowels of the earth, and fermenting with minerals, or escaping intothe atmosphere, where they ferment with acid vapours fitted to promote fermentation.
In explaining the structure of solid bodies, he is of opinion "that the smallest particles of matter may cohere by the strongest attractions, and compose bigger particles of weaker virtue; and many of these may cohere and compose bigger particles whose virtue is still weaker; and so on for divers successions, until the progression end in the biggest particles, on which the operations in chemistry, and the colours of natural bodies, depend, and which, by adhering, compose bodies of a sensible magnitude. If the body is compact, and bends or yields inward to pression, without any sliding of its parts, it is hard and elastic, returning to its figure with a force arising from the mutual attraction of its parts. If the parts slide upon one another, the body is malleable or soft. If they slip easily, and are of a fit size to be agitated by heat, and the heat is big enough to keep them in agitation, the body is fluid; and if it be apt to stick to things, it is humid; and the drops of every fluid affect a round figure, by the mutual attraction of their parts, as the globe of the earth and sea affects a round figure, by the mutual attraction of its parts by gravity."
Sir Isaac then supposes, that, as the attractive force of bodies can reach but to a small distance from them, "a repulsive virtue ought to succeed;" and he considers such a virtue as following from the reflexion and inflexions of the rays of light, the rays being repelled by bodies in both these cases without the immediate contact of the reflecting or inflecting body, and also from the emission of light, the ray, as soon as it is shaken off from a shining body by the vibrating motion of the parts of the body, getting beyond the reach of attraction, and being driven away with exceeding great velocity by the force of reflexion, the force that turns it back in reflexion being sufiicient to emit it.
We have already seen that Newton at one period of his life was a believer in alchemy, and that he even devoted much time to the study and practice of its processes. The Rev. Mr. Law has stated that there were found among Sir Isaac's papers large extracts out of Jacob Behmen's works, written with his own hand, and that he had learned from undoubted authority, that in a former part of his life he was led into a search of the philosopher's tincture from the same author. He afterwards stated in a private letter, that his vouchers are names well known, and that they have assured him that "Sir Isaac was formerly so deep in Jacob Behmen, that he, together with Dr. Newton his relative, set up furnaces, and were for several months at work in quest of the tincture." That this statement is substantially true is proved by Dr. Newton's own letter. We have seen in Sir Isaac's handwriting, The Metamorphoses of the Planets, by John De Monte Snyders, in 62 pages, 4to, and a key to the same work, and numerous pages of alchemist poetry from Norton's Ordinal, and Basil Valentine's Mystery of the Microcosm. There is also a copy of Secrets Revealed, or an open entrance to the Shut Palace of the King, which is covered with notes in Sir Isaac's hand, inwhich great changes are made upon the language and meaning of the thirty-five chapters of which it consists. I have found also among Sir Isaac's papers, a beautifully written, but incomplete copy of William Yworth's Processus Mysterii magni Philosophicus, and also a small manuscript in his handwriting, entitled Thesaurus Thesaurorum sive Medicina Aurea.
There is no problem of more difficult solution than that which relates to the belief in alchemy, and to the practice of its arts, by men of high character and lofty attainments. When we consider that a gas, a fluid, and a solid may consist of the very same ingredients in different proportions; that the same elements, with one or more atoms of water, form different substances; that a virulent poison may differ from the most wholesome food only in the difference of quantity of the very same ingredients; that gold and silver, and indeed all the metals, may be extracted from transparent crystals, which scarcely differ in their appearance from a piece of common salt, or a bit of sugar-candy; — that Aluminum, a metal with almost all the valuable properties of gold and platinum, can be extracted from clay; — that lights of the most dazzling colours can be obtained from the combustion of colourless salts; that gas, giving the most brilliant light, resides in a lump of coal or a block of wood; that several of the gems can be crystallized from their elements; and that diamond is nothing more than charcoal, — we need not wonder that the most extravagant expectations were entertained of procuring from the basest materials theprecious metals and the noblest gems. In the daily experiments of the alchemist, his aspirations, after great discoveries, must often have been encouraged by the singular phenomena which he encountered, and the startling results at which he arrived. The most ignorant compounder of simples could hardly fail to witness the almost magical transformations of chemical bodies, and every new product which he obtained must have added to the probability that the tempting doublet of gold and silver would be thrown from the dice-box with which he gambled. When any of the precious metals were actually obtained from the ores of lead and other minerals, it was not unreasonable to suppose that they had been formed during the process, and men not disposed to speculate might have thus embarked in new adventures to procure a more copious supply, without any insult being offered to sober reason, or any injury inflicted on sound morality.
Nor were the expectations of the alchemists to find a universal medicine altogether irrational and useless. The success of the Arabian physicians in the use of mercurial preparations naturally led to the belief that other medicines, still more general in their application, and more efficacious in their healing powers, might yet be brought to light, and we have no doubt that many important discoveries were the result of such overstrained expectations; but when the alchemists pretended to have obtained such a medicine, and to have conferred longevity by administering it, they did equal violence to reason and to truth.
When a mind ardent and ambitious is fascinated by some lofty pursuit where gold is the object, and fame the impulse, it is difficult to pause even after successive failures, and to make a voluntary shipwreck of the reputation which has been staked. Hope still cheers the aspirant from failure to failure, till the loss of fortune and the decay of credit disturb the serenity of his mind, and hurry him on to the last resource of baffled ingenuity and disappointed ambition. The philosopher thus becomes an impostor, and, by the pretended transmutation of the baser metals into gold, or the discovery of the philosopher's stone, or of the universal medicine, he attempts to sustain his sinking reputation, and recover the character he has lost. The communication of the great mystery is now the staple commodity with which he is to barter. It can be imparted only to a chosen few, — to those among the opulent who merit it by their virtues, and can acquire it by their diligence, and the divine vengeance is threatened against its disclosure. A process thus commencing in fraud and terminating in mysticism, is conveyed to the wealthy aspirant, or to the young enthusiast, and the grand mystery passes current for a season, till some wary professor of the art denounces its publication as detrimental to society.
The alchemy of Boyle, Newton, and Locke cannot be thus characterized. The ambition neither of wealth nor of praise prompted their studies, and we may safely say that a love of truth alone, a desire to make new discoveries in chemistry, and a wish to test the extraordinary pretensions of their predecessors and their contemporaries, were the only motives by which they were actuated. In so far as Newton's inquiries were limited to the transmutation and multiplication of metals, and even to the discovery of the universal tincture, we may find some apology for his researches; but we cannot understand how a mind of such power, and so nobly occupied with theabstractions of geometry, and the study of the material world, could stoop to be even the copyist of the most contemptible alchemical poetry, and the annotator of a work, the obvious production of a fool and a knave. Such, however, was the taste of the century in which Newton lived, and, when we denounce the mental epidemics of a past age, we may find some palliation of them in those of our own times.
Lady Mary Wortley Montague informs us, that "at Vienna there was a prodigious number of alchemists. The philosopher's stone," she says, "is the great object of zeal and science; and those who have more reading and capacity than the vulgar, have transported their superstition, (shall I call it?) or fanaticism from religion to chemistry; and they believe in a new kind of transubstantiation, which is designed to make the laity as rich as the other kind has made the priesthood. This pestilential passion has already ruined several great houses. There is scarcely a man of opulence or fashion that has not an alchemist in his service; and even the Emperor is supposed to be no enemy to this folly in secret, though he has pretended to discourage it in public."
In these times, and even earlier, Sir Isaac Newton lived. Leibnitz, his great rival, was also an alchemist. In his early life he was secretary to the Society of Rosicrucians at Nuremberg, — a secret association which practised alchemy, and which existed in several of the larger towns in Germany. Leibnitz, however, soon renounced his faith in the mystic art, and, there is reason to believe, from one of Newton's letters to Locke, thathe also had learned to have but little confidence even in the humbler department of the multiplication of metals.
See Vol. I. APPENDIX, pp. 388, 389.
Jan. 18th and 19th 1671-2, Newtoni Opera, tom. iv. pp. 273, 274. I find records of experiments in Dec. 10-19, 1678, and also in 1679, 1680.
See APPENDIX, No. XXXI.
See pages 120 and 121 of this volume.
Between the 10th and 30th December 1692. See Journal des Savans, 1832, p. 332.
Entitled Experiments and Observations, Dec. 1692, April and June 1693.
Phil. Trans. for March and April 1701, p. 824.
This constant recurrence to the fatal attack of 1693, which is synonymous with the fire in the laboratory, in order to fix the date of Newton's writings and discoveries, is equally painful and unjust. The date of the fire itself is actually unknown.
These queries are Nos. 6, 7, 8, 9, 10, 11, and 31.
In his Appeal to all that doubt or disbelieve the truths of the Gospel, 3d edit. p. 314, Mr. Law had stated that Sir Isaac Newton borrowed his doctrine of attraction from Behmen's Teutonic Theosopher. A correspondent having expressed a desire to know "the foundation which Mr. Law had for such an assertion," a friend of Mr. Law's replied to this application, and quoted from a letter of Mr. Law's to himself the statement which we have given in the text. The correspondent, in a subsequent communication, expresses his disbelief that Sir Isaac could have betrayed such weakness. See Gentleman's Magazine, 1782, vol. lii. pp. 227, 329, and 575.
See page 96 of this volume.
By W. C., Lond. 1669, 8vo. "Composed by a most famous Englishman, styling himself Anonymus or Eurœneus Philaletha, who, by inspiration and reading, attained to the philosopher's stone at his age of twenty-three years. Anno Domini, 1645."
In addition to these works, Sir Isaac has left behind him, in his Note-books, and separate MSS., copious extracts from the writings of the alchemists of all ages, and a very large Index Chemicus and Supplementum Indicis Chemici, with minute references to the different subjects to which they relate.
In a letter dated January 2, 1717, and supposed to be written to the Abbé Conti. — Letters and Works, vol. ii. p. 130.
See p. 121 of this volume.
When Locke, as one of the executors of Boyle, was about to publish some of his works, Newton wished him to insert the second and third part of one of Boyle's recipes, (the first part of which was to obtain "a mercury that would grow hot with gold,") and which Boyle had communicated to him on condition that they should be published after his death. In making this request, Newton "desired that it might not be known that they came through his hands." And he adds, — "One of them seems to be a considerable experiment, and may prove of good use in medicine in analysing bodies. The other is only a knack. In dissuading you from too hasty a trial of this recipe, I have forborne to say anything against multiplication in general, because you seem persuaded of it, though there is one argument against it which I could never find an answer to, and which, if you will let me have your opinion about it, I will send you in my next." Letter to Locke, August 2, 1692. — King's Life of Locke, vol. i. pp. 410, 413.
Even at the beginning of the present century, some distinguished individuals thought favourably of alchemy. Professor Robison, in writing to James Watt, says, "The analysis of alkalis and alkaline earths will presently lead, I think, to the doctrine of a reciprocal convertibility of all things into all. . . . I expect to see alchymy revive, and be as universally studied as ever." Feb. 11, 1800. — Muirhead's Origin and Progress of the Mechanical Inventions of James Watt, vol. ii, pp. 271, 272. Lond. 1854.