The earliest contributions to the Philosophical Transactions
“You” might have been his father, who was convenient, though here an informal way of communicating would have been more natural. Among other possibile correspondents is the longtime family friend William Heberden
A variety of evidence points to John Canton, a schoolmaster in Spital Square, as Cavendish’s correspondent. Thirteen years older than Cavendish, Canton was elected fellow of the Royal Society in 1749, and he began publishing his experiments in the Philosophical Transactions four years later. Cavendish had a connection with Canton through his father, who in 1762 confirmed Canton’s proof of the compressibility of water, discussed earlier. In 1766 Cavendish wrote to Canton about a book on electricity, establishing that the two had a connection by then; electricity was a major interest for both of them. The second possible evidence is an undated manuscript by Cavendish, “Paper Communicated to Dr Priestley,” in which Cavendish referred to what Priestley wrote about mephitic air in 1767, which he would have got personally from Watson or Canton, probably the latter.7 In his manuscript “Experiments on Heat,” Cavendish left a clue concerning the identity of a correspondent “you,” which fits Canton. Cavendish said that a certain substance differed from other substances by not transmitting heat as fast, commenting on his choice of the word “transmitting“: “I forbear to use the word conducting as I know you have an aversion to the word, but perhaps you will say the word I use is as bad as that I forbear.”8 Fluids are conducted; if heat, as Cavendish thought, is not a fluid, “conduction” conveys a false idea, implying that his reader “you” accepted the idea of heat as the motion of particles, narrowing the circle of potential correspondents. In a paper in 1768, Canton showed that he regarded heat as the agitation of the parts of bodies.9 Canton was generally interested in Cavendish’s subject, heat, studying its effect on diverse phenomena: magnetic strength, electrical conduction in solids and air, absorption of electric fluid in solids, and emission of light in phosphorescence and luminescence.
The persons mentioned so far were capable of serving as a sounding board for Cavendish’s experiments but probably not for his mathematics. At the bottom of the last page of a carefully drafted paper on the motion of sounds, Cavendish added a note addressed to “you,” mentioning a demonstration, “which if you have a mind I will show you.”10 A possible mathematical reader for this paper was John Michell
As a special case, we consider one more possibile correspondent, John Hadley
Given the range of his researches, Cavendish likely had more than one correspondent. Considering that his scientific manuscripts contain no responses to his early researches, it is conceivable that he did not send his work to anyone but simply adopted the form of the letter-report from the Philosophical Transactions. In the absence of more revealing documents, we can only speculate about his correspondents
By all accounts Cavendish cut an awkward figure in public. He did not do so at home, where everything was made to fit. Furnished with instruments and books, his home was the principal location of his chosen life. The gentleman’s double house on Great Marlborough Street
Ever since Wilson’s
Cavendish typically began an experiment with carefully weighed quantities of substances, which he then combined and performed various operations on, and the products he obtained he would again weigh. He might then put the products through a series of tests, “small experiments” as he called them, in which he did not record, and probably did not measure, the quantities involved. As he proceeded, he described
Chemistry in the middle of the eighteenth century was still closely tied to pharmacy, medicine, metallurgy, and manufactures, but it had a strong scientific direction too. A major scientific source was the work of Johann Joachim Becher
An advantage of phlogiston chemistry was its unified explanation of combustion and of the calcination of metals (the transformation of metals by intense heating or by chemical combination into a powder having the properties of an earth). When combustibles such as charcoal burn, their phlogiston separates and flies off, the evidence for which is obvious to the senses. When metals, which like combustibles contain phlogiston in combination with another constituent, are calcined they lose their phlogiston, and when the calces are heated with charcoal they reacquire phlogiston, returning to pure metals. Phlogiston, by its presence or its absence, affects most chemical reactions, and by keeping a balance, the chemist could foresee the outcome. The experimental proof of phlogiston seemed incontravertible, the reason why the physical school of chemistry accepted it. However indispensable it was in understanding chemical operations, phlogiston by itself was elusive, thought to be the “least accurately known” of chemical substances or principles and incapable of being isolated and studied on its own.19 Cavendish would disagree on this important point.
When Cavendish took up chemistry, phlogiston was familiar in Germany, but in Britain and France it was just taking hold. Interest in phlogiston in France was stimulated especially by translations of Becher’s and Stahl’s writings by Guillaume-François Rouelle
By the time of his experiments on arsenic, Cavendish had been coming to meetings of the Royal Society for about seven years, five years as a member, during which time he had heard few reports or read few papers dealing with chemical topics in the Philosophical Transactions, and none relevant to the work in question.27 The Londoner Cavendish, who was just then setting out on chemical research, would have consulted books and papers from abroad, written in the foreign languages he could read, Latin, French, and German, or else in English translation. His point of departure was the French chemist Pierre Joseph Macquer’s
In this, his most important early work, Macquer distilled arsenic with nitre (potassium nitrate), leaving as residue a compact, white, soluble, mild salt, the neutral arsenical salt. The salt had obvious value for scientific chemistry, and it probably had practical uses, though Macquer doubted that these included medicine despite its actual mildness, since the “name of arsenic is so terrible.”29 The agonizing symptoms and fatal consequences of arsenic were mentioned in every book of chemistry. The German chemist Caspar Neumann
When Cavendish took up the study of arsenic, chemists had not been able to “determine what it really is, or to what class of bodies it belongs.”31 Independently of its noxious properties, arsenic has “singular properties, which render it the only one of its kind.” It was the “very singular and extremely different” properties of arsenic from those of other metallic calces that led Macquer to investigate this little-known calx in the first place.32 Neither fish nor fowl, but something of a flying fish, arsenic behaves like a metal in some states and like a salt in other states. On the one hand, like every metallic calx, “arsenic” can be changed into a metallic form, a “true semi-metal,” or “regulus of arsenic,” by combining it with phlogiston. On the other hand, like salts, arsenic is soluble in water. Even when it is regarded as a salt, arsenic is uncommon, neither acidic nor alkaline, yet it behaves as if it were an acid.33 When it is considered as a calx, arsenic differs from other known calces: it is volatile with a strong smell, it is fusible, it unites with metals and semi-metals, and—the difference that Macquer and Cavendish picked up on—it decomposes nitre when distilled with it.34 From the standpoint of its readiness to unite with other substances, arsenic is exceptional too.35 Cavendish did not say why he investigated arsenic, but from the state of chemistry at the time, we get an idea of its considerable interest, at once dangerous, difficult, unique, scientifically puzzling, and incompletely known.36 Its study demanded manipulative skills of a high order, a stiff challenge and testing ground for a young chemist.
In practice, chemistry looked complicated because it dealt with all kinds of matter with a large repertoire of operations. In principle, chemistry looked simple, though this appearance was changing. “Neutral salts,”
Cavendish examined the action of several acids and alkalies on arsenic
In going from a first draft to a revised draft of his paper on arsenic, Cavendish made revealing changes of wording. Whereas in the first draft he expressed his opinions such as his differences with Macquer
We look next at Cavendish’s other surviving early chemical research, probably carried out about the same time.43 The subject was tartar
In his experiments on tartar, Cavendish made use of equivalent weights
Both arsenical acid and tartaric acid became known to chemists through publications in the 1770s by the Swedish chemist Carl Wilhelm Scheele
Air was studied scientifically in the seventeenth century by Boyle
We begin where we left off, with Cavendish’s early experiments on tartar. In his Treatise on […] Air, Tiberius Cavallo
The connection is also evident in his first chemical work to be laid before the Royal Society, in 1764, two years before his paper on factitious air. William Heberden’s
We can see why Joseph Black was important to Cavendish
Black and Cavendish were similar in a number of ways. Both were methodical, unaffected, cautious in their reasoning, exacting in their research, and alert to careless error. Cavendish was rich, and Black was well-to-do. Both led outwardly uneventful lives. Both made chemistry and heat major fields of research, and in both fields they began with the same subjects, factitious air and specific and latent heats. Both were reluctant to publish, Black even more so than Cavendish. They both shirked correspondence. Otherwise, in their dealings with people, they were not alike. Cavendish was difficult to engage in conversation, and uninterested in any subject that was not scientific. Black was affable, always ready to enter into conversation, serious or trivial. For the whole of his career, Black was a professor, who lectured on his discoveries. If Cavendish had been a professor, his researches, like Black’s, would have been spread by his students, and he would have had greater influence on the course of science in the eighteenth century. So far as we know, Black and Cavendish never met.55
Black’s originality began with his observation that when subjected to fire, magnesia alba loses a substantial proportion of its weight and that the lost portion is mainly a kind of air, or gas (carbon dioxide); he further observed that the loss of weight is recovered when the calcined magnesia alba, a caustic substance he called magnesia usta (magnesium oxide), is recombined with the same air. He showed that this same air, “fixed air” (Hales’s term), is found in other alkalis such as chalk (calcium carbonate); when caustic quicklime, which is produced by calcining chalk with heat, is combined with fixed air (not directly but through a series of steps involving slaked lime, potash, and caustic potash), the chalk is recovered. Black
Cavendish’s first scientific publication under his own name appeared in 1766 in the Philosophical Transactions, an exacting investigation of an experimental field, pneumatic chemistry
For the kind of study it was, Cavendish’s paper was unusual, as a glance at the journal shows. His paper was preceded by one by John Michell on determining the degree of longitude at the equator and by a paper on an uncommonly large hernia and followed by an account of the Polish cochineal and four more papers about animals. Cavendish’s second paper, in 1767, appeared in similar mixed company: an account of men “eight feet tall, most considerably more” observed near the Straits of Magellan in the country of Patagonia, an account of a locked jaw and a paralysis cured by electricity, and an account of a meteor and another about a swarm of gnats seen at Oxford. In the context, Cavendish’s reports of laboratory precision were perhaps the most remarkable.
Instead of the term “factitious” air, Cavendish could have used “fixed,” since the usual meaning of “fixed air” then was any sort of air contained in bodies, but he wanted to retain the specific meaning for “fixed air” that Black had used for the air he studied. To avoid confusion Cavendish borrowed Boyle’s
The paper was three papers published as one, as the title says, “Three Papers, Containing Experiments on Factitious Air.” The first paper was received by the Royal Society on 12 May and read on 29 May 1766, on the eve of the long summer recess, and the second and third papers were read on two successive meetings after the recess, on 6 and 13 November. Cavendish drafted a fourth paper but withheld it. The papers, the three published ones and the unpublished fourth, formed a series, their experiments relating to each other by subject, method, apparatus, and theory. Each addressed a certain kind of factitious air
8.3 Factitious Air Apparatus. The numbered figures are from Cavendish’s first publication, for which he received the Royal Society’s Copley Medal. Figure 1 shows his technique for filling a bottle D with air. The bottle, containing water, is inverted in the vessel of water E; the air to be captured is generated by dissolving metals by acids and by other means in bottle A. The measure of quantity of air is the weight of the water it displaces in D. Figure 2 shows how air is transferred from one bottle to another. Figure 3 shows how air is withdrawn from a bottle by means of a bladder. The speckled substance in Figures 4 and 5 is dry pearl ash, through which air is passed to free it from water and acid. Cavendish (1766).
Part II of Cavendish’s paper is about “fixed air,”
Cavendish’s point of departure in Part III was a study of fermented and putrefied substances by Macbride in 1764. Finding that “fixed air” was given off, Macbride concluded that this air plays an essential role as the cement of living bodies. He took his understanding of air from Hales, and in citing Black, he made Black’s apparatus and work better known. This was his main contribution to pneumatic chemistry, his interest in the subject being primarily medical and physiological.64 Cavendish wanted to know if fermentation and putrefaction yielded any factitious air other than what Macbride found, Black’s fixed air. He discovered that the air produced by fermenting brown sugar and apple juice with yeast was the same as that produced from marble by solution in acids, “fixed air.” The air he obtained from putrefying gravy broth and raw meat he found to be a mixture of fixed air and inflammable air, neither pure.65
In Part IV, Cavendish
For his experiments on factitious air, Cavendish was awarded the Copley Medal of the Royal Society
In Cavendish’s study of factitious air
We look at Cavendish’s view of phlogiston
A counter argument can be made. First, there was Cavendish’s cautious wording: in 1766 he wrote that phlogiston “forms,” not “is,” inflammable air. Second, chemists who later identified phlogiston with inflammable air did not credit Cavendish with the idea. In 1782, Richard Kirwan
Following the work of Black, in his first published paper Cavendish helped to discredit the ancient idea of a single, a universal air. He showed that inflammable air
Cavendish’s contribution to pneumatic chemistry
In the following year, 1767, Cavendish published an analysis of water obtained from a location near Soho Square, Rathbone-Place.83 Having a practical use, mineral water
The occasion for his study would seem to have been a paper in the Philosophical Transactions in 1765 by William Brownrigg
Produced by a spring, Rathbone-Place water until a few years before had been raised by an engine for public distribution in the neighborhood. Now a pump remained, from which Cavendish drew his sample, which he described as “foul to the eye,” forming a “scurf” over time. To see if what Brownrigg
Cavendish’s analysis of a mineral water
By Cavendish’s time, the craft of instrument making was highly advanced. Aided by improvements in materials and the graduation of scales, instrument makers kept up with (and stimulated) the demand for better instruments.91 Living in a city with a flourishing trade in instruments, Cavendish could conveniently inspect, buy, and commission the thermometers, telescopes, and other tools he needed for his research. At some stage, he employed an instrument maker of his own. His interest and skill were recognized by the Royal Society, which regarded him as its resident authority on matters having to do with instruments of all kinds.
Because he was wealthy, Cavendish could buy any instrument he wanted, and because his scientific interests were wide-ranging, he owned a large number of them
Accurate measurements in Cavendish’s main experimental fields, electricity, chemistry, and heat, and in his main observational field, meteorology, began to become important around the time he began to do research, the 1760s and 70s. Researchers did not yet depend on great accuracy
All instruments are imperfect in their infancy, J.A. Deluc
To see how Cavendish worked with instruments
Like many other serious students of the weather before and after him, Cavendish
A specific reason why Cavendish commissioned Nairne and Blunt to build a wind measurer may have been that they had recently built a portable wind gauge for use at sea for James Lind, physician to George III. This instrument was the best of its kind, which was the kind of nearly all early wind gauges. They were, in effect, pressure gauges, used by seamen who were interested in that property of the wind, its pressure.101 The inspiration of Cavendish’s earliest experiments may have come from Alexander Brice
There had long been instruments for tracking the weather—weather vane, rain catch, and even a crude indicator of humidity—but these did not make the study of the weather scientific. By Cavendish’s time, it was understood that a science of the weather required measuring instruments capable of reasonable accuracy. Besides the barometer
The rudimentary state of thermometry at the beginning of the eighteenth century is suggested by Newton’s
The Royal Society
There does not seem in all philosophy any thing of more immediate concernment to us, than the state of the weather.… To establish a proper theory of the weather, it would be necessary to have registers carefully kept in divers parts of the globe, for a long series of years; from whence we might be enabled to determine the direction, breadth, and bounds of the winds, and of the weather they bring with them.… We might thus in time learn to foretell many great emergencies; as, extraordinary heats, rains, frosts, draughts, dearths, and even plagues, and other epidemical diseases.117
At once a challenge to science and a vital issue to humanity, the weather was the kind of problem the Royal Society regarded as its reason for being, meteorology embodying its early belief in the advancement of science and human welfare through natural histories. The means in the late eighteenth century was weather registers like the Royal Society’s.
To keep the register, Cavendish directed the clerk of the Society to read the barometer and indoor and outdoor thermometers
The Royal Society’s “Meteorological Journal,” as Cavendish called it, was a conventional journal in the features of the weather it reported: temperatures, pressures, and the like. It did not contain a chemical column for the composition of atmospheric air, and in a few years Cavendish would show that there was no need for such a column, for the composition was unchanging. Nor did it contain electrical columns, though there was some interest in this. Recently the atmosphere had taken on a new complexity and interest as an electrical medium, and prosaic events such as fog and falling weather and spectacular phenomena such as lightning, thunder, auroras, meteors, earthquakes were observed with that in mind. William Henly
Even without the complications of electrical and upper-air measurements, the keeping of the Royal Society’s weather register was demanding, requiring the clerk to make multiple observations at different times of the day. Less confining would have been fully automatic clock-driven instruments, which were already an old idea. Christopher Wren
8.4 Register Thermometer
8.5 Apparatus for Adjusting the Boiling Point. The committee of the Royal Society, which Cavendish chaired, conducted experiments to determine the regularity of the boiling point. ABCD is the pot, AB the cover, E the chimney to carry off steam, FG the thermometer fitted tightly to the cover. The stem of the thermometer as well as the ball are immersed in steam, not water, in accord with Cavendish’s recommendation. The committee recommended this apparatus, including an almost identical drawing, in its published paper. “The Report of the Committee Appointed by the Royal Society to Consider of the Best Method of Adjusting the Fixed Points of Thermometers; and of the Precautions Necessary to Be Used in Making Experiments with Those Instruments,” PT 67 (1777): 816–857, opposite 856. The drawing by Cavendish is in Cavendish Mss III(a), 2. Reproduced by permission of the Trustees of the Chatsworth Settlement.
In 1776 Cavendish together with Aubert, Maskelyne
We return to Cavendish’s garden and magnetic instruments. Like the weather, the Earth’s magnetism varies complexly from place to place and from time to time, periodically and secularly. Cavendish observed the Earth’s magnetic variation
We have chosen meteorology as a source of examples to show Cavendish’s way with instruments. Whoever examines his meteorological manuscripts must be struck by the tenacity with which he compared his instruments
In Cavendish’s day it was common for researchers to build some of their apparatus
Cavendish’s examination of Nairne and Blunt’s
Paul T. Costa, Jr., and Robert R. McCrae (1994, 21–22).
Cavendish’s editor Thorpe refers to “an interpolation table calculated by Cavendish, from the results of measurements made in conjunction with his father on the Tension of Aqueous Vapor…. They appear to have been made about 1757 and are based upon a number of observations over a considerable range of atmospheric temperature and probably, therefore, at various seasons of the year.” If Thorpe is correct about the year, they are the earliest experiments of Henry Cavendish’s we have record of. Sci. Pap. 2: 355.
Charles Bazerman (1988, 130, 137).
Roderick W. Home (1972)
On 20 Apr., 4 and 11 May, 8 June, 9 Nov. 1769, JB, Royal Society 26.
Henry Cavendish, “Paper Communicated to Dr Priestley,” Scientific Mss, Misc. The paper is directed to “you,” who is either Canton or Watson, most likely the former, who would have passed it along to Priestley. At this time, Cavendish did not know Priestley, who lived in Leeds, and Canton who knew Priestley lived in London. Two letters Priestley wrote to Canton in 1767 refer to Priestley’s experiments on mephitic air. Joseph Priestley to John Canton, 27 Sep., 12 Nov. 1767, in Joseph Priestley (1966, 58).
Henry Cavendish, section of “Experiments on Heat,” entitled “Experiments to Shew That Bodies in Changing from a Solid State to a Fluid State Produce Cold and in Changing from a Fluid to a Solid State Produce Heat,” Sci. Pap. 2:348–50, on 350.
John Canton (1768, 342–343).
Henry Cavendish, “On the Motion of Sounds,” Cavendish Mss VI(b), 35:10.
“Hadley, John,” DNB, 1st ed. 8:878–880, on 879.
John Twigg (1987, 212–213). John Hadley (1758). At Trinity College, Cambridge, there is a two-volume manuscript of Hadley’s lectures: “An Introduction to Chemistry, Being the Substance of a Course of Lectures Read Two Years Successively in the Laboratory at Cambridge by John Hadley ….” “Hadley, John,” 879.
Hadley’s work is referred to in a footnote to the unpublished fourth part of Cavendish’s paper on factitious air in 1766. “Experiments on Factitious Air. Part IV. Containing Experiments on the Air Produced from Vegetable and Animal Substances by Distillation,” Sci. Pap. 2:307–316, on 313.
Hadley wrote to the secretary of the Royal Society that the analysis of mineral water was “very difficult & would lead into very extensive chemical inquiries, “and his own papers on it were “not of consequence enough to be printed.” John Hadley to Thomas Birch, 13 Sep. 1762, BL Add Mss 4309, f. 9.
We have been guided in our sketch of Cavendish’s laboratory by the entry “Laboratory (Chemical)” in Pierre Joseph Macquer’s Dictionary of Chemistry, originally published in 1766, just after Cavendish had begun his known chemical experiments. Macquer’s laboratory was intended for the “philosophical chemist,” and together with his list of reagents, it sufficed for “any chemical experiment.” P.J. Macquer (1771). A more detailed itemization of apparatus divided into items used in preparation of operations and items used in operations is given in Peter Shaw and Francis Hawksbee (1731, 19–21).
James Keir, “Preface,” iii, in his translation in 1771 of Macquer’s Dictionary of Chemistry.
Maurice Crosland (1963, 408, 440).
Mi Gyung Kim (2003, 203). Antoine Baumé (1763, 41–44). Crosland (1963, 408).
Thomas Thomson (1830–1831, 2:257–260). Macquer (1771, 2:516).
Thomas L. Hankins (1985, 95). Henry Guerlac (1959, 103).
W.A. Smeaton (1975, 619). Macquer’s Élémens de chymie théorique (Paris, 1749) and Élémens de chymie practique […] (Paris, 1751) were brought out in English translation by Andrew Reid in 1758 as Elements of the Theory and Practice of Chemistry. Casper Neumann (1759). Nathan Sivin (1962, 73).
Quotation from p. 8 of Hadley’s lectures. L.J.M. Coleby (1952a, 295).
Quoted in John Pearson (1983, 118).
The earliest chemical work by Cavendish for which there is an apparently complete record consists of the following: a bundle of 59 numbered pages of laboratory notes on arsenic, with index; a carefully written 25 page version of the account; and 19 unnumbered pages constituting a rough draft. Cavendish Mss II, 1(a), 1(b), and 1(c). A brief description and analysis of these papers is given by Thorpe, in Cavendish, Sci. Pap. 2:298–301.
Henry Cavendish, “Arsenic,” Cavendish Mss II, 1(b):20, 25.
It was probably sometime after December 1764 that Cavendish wrote or at least completed the paper for “you.” To give an idea of the extensiveness of Hadley’s familiarity with arsenic, the topics he addressed under “Of Arsenic” in his lectures were: “The Orders of Arsenic; Cobalt, white Pyrites, Orpiment, Realgar. – Of white, yellow, and red Arsenic, and the Method of procuring them – Artificial Realgar, Orpiment fused – Regulus of Arsenic procured from Cobalt by Distillation – Zaffer and Smalts – Sympathetic ink made with Zaffer – Glass rendered Blue by fusing it with Zaffer – Acid of Niter procured by distilling Nitre with Arsenic – The Residuum considered – Arsenic fixed by fusing it with Nitre – Regulus of Arsenic deflagrated with Nitre – White Enamel of Arsenic – Reduction of Arsenic to its Reguline form – Butter, Oil, and Cinnabar of Arsenic, procured by distilling Orpiment with Corrosive Sublimate – Sympathetic Ink from Orpiment and Lime, and its use in discovering the adulterations of Wine by preparations of Lead.” Hadley (1758, 17–18).
In the years 1755–64, the Philosophical Transactions contained eight papers on “chemical philosophy” and two on “chemical arts,” according to the classifications used in the abridgment of the journal, which lists all papers appearing in the full journal. Five other papers were about natural waters, the subject which Cavendish would take up in his second published paper on chemistry.
Pierre Joseph Macquer, “Researches sur l’arsenic. Premier mémoire,” and “Second mémoire sur l’arsenic,” Mémoires de l’Académie des Royal Sciences, 1746 (published 1751), 223–236, and 1748 (published 1752), 35–50. Macquer described this work in 1766 in his Dictionary of Chemistry, translated in 1771. The article “Neutral Arsenic Salt” is in vol. 2, 666–667. Shortly before Cavendish’s researches on the subject, Macquer’s work on arsenic was described in English in an annotation by William Lewis to the translation of Casper Neumann (1759, 143). Coleby (1952a, 301).
Macquer (1771, 1:100, 2:666–667).
Neumann (1759, 145).
Ibid., 140–141. What Neumann, Macquer, Cavendish, and their contemporaries called “arsenic” is a dense, brittle substance with a crystalline or vitreous appearance; this substance, arsenious oxide, is a common byproduct of roasting metallic ores. Another name for it then, as now, is “white arsenic,” the calx of regulus of arsenic, the white, shiny semi-metal.
Pierre Joseph Macquer (1758, 1:96).
Macquer (1771, 2:634).
Arsenic has the least, or next to least, affinity of the soluble substances for the several acids, with the exception of aqua regia. Gellert’s “Table of the Solutions of Bodies,” at the end of vol. 2 of Macquer’s Dictionary.
For example, arsenic was soluble in acids, and the results had “not yet been sufficiently examined.” Macquer (1771, 1:103).
The Scottish chemist William Cullen’s table of twelve neutral salts was reproduced in Donald Monro (1767). Monro, on page 483, pointed out that a table had been published in Germany giving three or four more of these salts, and that there were actually many more because vegetable acid was in reality many acids each with its own neutral salts.
Macquer (1771, 2:642, 649).
Cavendish, “Arsenic,” 1(b), 10, 13. Thorpe, in Cavendish, Sci. Pap. 2:299. A.J. Berry (1960, 46–47).
We see the chemist’s dependence on many reagents and testing materials in Cavendish’s study of arsenic. From his well-supplied laboratory, he made use of (in his spelling) distilled vinegar, spirits of salt (hydrochloric acid), oil of vitriol (sulfuric acid), spirit of nitre (nitric acid), aqua fortis (concentrated nitric acid), nitre, syrup of violet (a botanical extract that changes color when exposed to acids or alkalis), tournsol paper (litmus paper, a mix of dyes that turns color when exposed to acids or alkalis), blue vitriol (copper sulfate), green vitriol (ferrous sulfate), solutions of silver, mercury, copper, and iron in nitric acid, solutions of mercury, copper, and iron in concentrated nitric acid, solution of tin in hydrochloric acid, solutions of gold and nickel in aqua regia (mixture of nitric and hydrochloric acids), solution of regulus of cobalt, sope leys (potassium hydroxide), pearl ashes (potash), fixed alkali (potassium carbonate), calcareous earth (whiting, or carbonate of lime), volatile alkali (ammonia), magnesia, earth of alum, sedative salt (boric acid), white flux, sulphur, linseed oil, and charcoal. Cavendish also had at hand pure “rain” water.
Macquer wrote: “Nothing can equal the impetuosity with which nitrous acid joins itself to phlogiston” (1771, 1:11). Cavendish, “Arsenic,” 1(b), 19–20.
Cavendish made the acid or, in effect, the same thing, the neutral arsenical salt, three ways: distilling arsenic with nitre, dissolving arsenic in concentrated spirit of nitre, and heating arsenic with fixed alkali. All three ways had the same rationale: the effect of exposing a metal (for that is how he regarded arsenic) to an acid or to heat and open air was to deprive it of its phlogiston. “Arsenic,” 1(b), 16.
Cavendish performed two sets of experiments on tartar, neither carrying a date, described on unnumbered sheets: “old experiments on tartar,” 10 ff., and “new experiments on tartar,” 24 ff., plus 6 more sheets. Cavendish Mss II, 2(a) and 2(b), respectively.
Macquer (1771, 1:771–772).
Thorpe, in Cavendish, Sci. Pap. 2:301. Cavendish “discovered the true nature of cream of tartar … and its relation to soluble tartar”: J.R. Partington (1957, 104).
Thomson (1830–1831, 1:271).
Coleby (1952a, 295).
Thorpe, in Cavendish, Sci. Pap. 2:304.
Carl Wilhelm Scheele (1786). Partington (1961–62, 1964, 2:729). Thomson (1830–1831, 2:63). Thorpe surmises that Cavendish’s later experiments might have followed Scheele’s paper on tartaric acid in 1769, though they could have been earlier, a possible reason he did not publish his own. Cavendish, Sci. Pap. 2:302.
Aaron J. Ihde (1964, 30–38).
Tiberius Cavallo (1781, 594–596, 606–608).
The title of the paper is not Cavendish’s, and in the end he did not publish it. It generalized the conclusion he had arrived at in the published part of his paper on factitious air, which is that acids deprive metals of their phlogiston, which flies off with the acid. His earliest chemical experiments on arsenic have substantial overlap with his study of factitious air through their common concern with phlogiston, metals, acids, and aerial substances.
William Heberden (1765). This paper was read at the Royal Society on 7 Feb. 1764.
William Ramsay (1918, 4–5, 14–15). Henry Guerlac (1957, 433–434).
Ramsay (1918, 1–2, 114–115, 133).
Henry Guerlac (1970, 2:173–183).
Guerlac (1957, 454–456).
Cavendish (1766, 77). Black gave a fuller description of “factitious air.” “Chemists have often observed, in their distillations, that part of the body has vanished from their senses, notwithstanding the utmost care to retain it; and they have always found, upon further inquiry, that subtle part to be air, which having been imprisoned in the body, under a solid form, was set free and rendered fluid and elastic by the fire.” Joseph Black (1898, 16).
Cavendish (1766, 83, 95–96; 1767, 105).
Stahl thought that a compound of phlogiston and an acid was inflammable. Thomson (1830–1831, 2:340).
29 May 1766, JB, Royal Society 25:876.
Cavendish (1766, 89, 91, 93).
E.L. Scott (1970, 46). Macbride’s Experimental Essays were published in 1764. Guerlac (1957, 454).
Cavendish (1766, 98–100).
Henry Cavendish, “Experiments on Air. Part IV,” Sci. Pap. 2:307–315.
Edward Delaval (1765).
Cavendish (1766, 100).
Cavendish, “On the Solution of Metals in Acids,” 305.
Cavendish (1766, 88).
Berry (1960, 51).
Cavendish (1766, 89).
The notion of significant figures had not taken hold everywhere. The chemist William Nicholson said that the best chemical balances were accurate to five or six places, according to claims made for them. In weighing an air, the error was thirty times as great in proportion to the whole as it was in weighing other substances. This means that if a balance was accurate to five places in common weighing, it was accurate to only three places in the case of an air, and because of the complications of temperature and pressure, the accuracy was probably less than three places. Lavoisier nonetheless gave the specific gravities of airs to five places, on which he made calculations to six or eight places, thousands of times their real accuracy in, what James Short (above) called a “pretense” of accuracy. Nicholson’s comments in his translation of the notes by French chemists to the French edition of Richard Kirwan (1789, vii–ix).
Cavendish (1766, 79).
Thomson (1830–1831, 2:340).
W. Vernon Harcourt (1839, 28).
Richard Kirwan (1782, 195–197).
Joseph Priestley (1783, 400).
In the footnote, Cavendish says that Hadley distilled the salt sal ammoniac with red lead, or lead oxide, and also with bare metal, and that the different results show that metals contain no fixed air, or carbon dioxide, and that metallic calces, or oxides, contain a great deal. He says that the reason that minium, another name for lead oxide, weighs more than the bare metal lead is that lead absorbs fixed air on being converted into minium. In the manuscript of Hadley’s lectures, we find what Cavendish refers to here: Hadley says that 100 pounds of lead give 110 pounds of minium, and that the increased weight is due to the fixed air united to the minium. The reference to Hadley shows that Cavendish and Hadley were aware that the increase in weight on the calcination (oxidation) of metals was a problem and that phlogiston, as they understood it, could not solve it: they thought (incorrectly) that fixed air (carbon dioxide) was the explanation. Hadley’s statement is based on Macquer’s book on the elements of chemistry, though Macquer does not give an explanation for the increase in weight, commenting only on the “numerous ingenious but not altogether satisfying explanations.” Hadley’s explanation takes into account the experiments on airs by Stephen Hales and Joseph Black. Page 208 of the manuscript lectures, quoted in Coleby (1952a, 299).
A.L. Donovan (1975, 219). J.R. Partington (1961–62, 3:316).
Thomson (1830–1831, 2:1, 343).
Ibid. 2:341. Joseph Priestley (1772b, 234–235).
Henry Cavendish (1767).
William Lewis, in Neumann (1759, 252–253).
This was in 1733. “Sir James Lowther, 4th Baronet.” Anon.,”William Brownrigg” (https://en.wikipedia.org/wiki/William_Brownrigg). Thomas Young (1816–1824, 436).
William Brownrigg (1765, 218–219, 238); on 336–343 is an extract from a paper read to the Royal Society in 1741, from which the new paper was written. J.V. Beckett (1977a, 255–258). J. Russell-Wood (1950, 436–438).
“Some Observations upon the Several Damps in the Coal Mines near Whitehaven by Dr Willm Brownrig Phisitian of that Town Communicated by Him to Sr James Lowther Bart,” Cavendish Scientific Manuscripts, Devon. Coll., Chatsworth, Misc. Hereafter Cavendish Mss.
Cavendish (1767, 105, 107).
Thomson (1830–1831, 2:344). Berry writes, “Truly indeed was Cavendish the founder of water analysis.” (1960, 57).
Torbern Bergman (1784, 109).
Maurice Daumas (1963, 421–424).
“Extracts from Valuations of Furniture,” A Catalogue of Sundry Very Curious and Valuable Mathematical, Philosophical, and Optical Instruments … Of a Gentleman Deceased … On Saturday the Fifteenth of June 1816, at Twelve O’clock, Devon. Coll.
Daumas (1963, 418, 428–430).
Jean André Deluc (1773, 430–432).
Jesse Ramsden (1779, 419).
Richard Kirwan (1787, v–vi).
Frederick Cavendish to Henry Cavendish 10 Sep. 1809; Henry Cavendish to Frederick Cavendish, n.d., draft; in Russell McCormmach (2014, 260).
William Herschel to Lord Salisbury, late Jan. 1789, Royal Astronomical Society, Mss Herschel, W 1/1, 170–171.
The account of Cavendish originated with the instrument maker John Newman, of Regent Street, in Wilson (1851, 179).
On Edward Nairne and Thomas Blunt: E.G.R. Taylor (1966, 62, 214, 256).
A. Wolf (1961, 1:320–323).
Wolf (1961, 1:324).
Henry Cavendish to “your Lordship,” undated, Cavendish Mss, Msc.
Wilson (1851, 179).
William E. Knowles Middleton (1969, 203). Before Robert Hooke, the Italian architect Leon Battista Alberti invented a mechanical wind measurer, consisting of a disc oriented perpendicularly to the wind mounted on an arm free to rotate. Hooke’s device was similar.
Henry Cavendish, “No. 1. Measurer of Wind,” and “Trial of Windgauge,” Cavendish Mss, Misc.
Cavendish to “your Lordship.”
Henry Cavendish (1776b).
9 Dec. 1773, Minutes of Council, Royal Society 6:202.
Richard Kirwan (1787, iii).
William E. Knowles Middleton (1966, 57–58).
Robert Smith, “The Editor’s Preface,” in Roger Cotes (1747).
Middleton (1966, 65, 75, 115). Britain and Scandinavia used the Fahrentheit scale, while on the Continent, the Réaumur, Delisle , and Swedish scales were used. Kirwan (1787, vi).
Henry Cavendish (1921a, 2:351–353); Cavendish (1776b, 115). William E. Knowles Middleton (1964, 132). Middleton dates the increase in accuracy of calibration from about 1770, the time we are considering.
The Council ordered the clerk of the Society to make daily observations of the weather “with the instruments to be procured for that purpose, & proper accommodations under the inspection of the Hon. Henry Cavendish.” 22 Nov. 1773, Minutes of Council, Royal Society 6:197.
J. Oliver (1969, 291).
Charles Hutton (1795–1796, 2:677).
“The following scheme drawn up by the Hon. Henry Cavendish for the regulating the manner of making daily meteorological observations by the Clerk of the Royal Society …,” 9 Dec. 1773, Minutes of Council, Royal Society, 6:200–204. “Meteorological Journal Kept at the House of the Royal Society, by Order of the President and Council,” PT 67 (1777): 357–384.
William Henly (1774, 426–427).
Middleton (1969, 254–255).
Henry Cavendish, “Clock for Keeping Register of Thermometer,” Cavendish Mss IV, 1.
This instrument was calibrated at Chatsworth in 1779, more or less dating it. Charles Cavendish could have designed it, but at that late date it was more likely Henry Cavendish, if it was not an instrument maker. Through Humphry Davy this instrument eventually passed to the Royal Institution, where it is kept in its collection of historical instruments. Middleton (1966, 138–139). Cavendish, Sci. Pap. 2:395–97. Among Cavendish’s manuscripts is “Thermometer for Greatest Heat by Inverting the End of Tube into a Movable Cyl. Of Spt. & Water,” Cavendish Mss III(a), 14(c).
14 Nov. 1776, Minutes of Council, Royal Society 6:303.
Middleton (1966, 116–117, 127). Douglas W. Freshfield and H.F. Montagnier (1920, 176–177).
Signed by Cavendish (listed first), Heberden, Aubert, Deluc, Maskelyne, Horsley, and Planta (1777).
Cavendish (1776b, 115).
Kirwan (1787, iv).
Middleton (1966, 128).
Cavendish (1776b, 117, 124–125).
Cavendish, “Horizontal Needle.” On page 3, alongside Cavendish’s readings taken in his garden, there are readings by Heberden, who must have been there too. Cavendish’s manuscripts also contain readings of the variation compass taken at Heberden’s house. Cavendish Mss IX, 19, 21, 23.
Henry Cavendish, “Observations of Magnetic Declination,” Cavendish Mss IX, 1. The earliest observations in this manuscript of 256 numbered pages were made at Hampstead; those from page 30 on were made on Clapham Common.
Henry Cavendish to J. Churchman, n.d. [after 12 July 1793], draft; in Jungnickel and McCormmach (1999, 694).
Cavendish’s manuscripts contain his instructions to an instrument maker. “Dipping Needle”; “Trials of Dipping Needle”; “On the Different Construction of Dipping Needles,” Cavendish Mss IX, 7, 11, and 40. He drew up directions for the use of the dipping needle for three voyages, by Richard Pickergill, James Cook and William Bayley, and Alexander Dalrymple. Ibid., 41–43.
Middleton (1964, 100). On Saussure and Deluc’s disagreements: Charles Blagden to Henry Cavendish, 23 Sep. 1787; in Jungnickel and McCormmach (1999, 641).
Middleton (1969, 103, 106).
Deluc (1773, 405).
John Smeaton (1771, 199).
Henry Cavendish, “Hygrometers,” Cavendish Mss IV, 5. This manuscript consists of 77 numbered pages of laboratory notes and an index.
George Shuckburgh (1779, 362).
29 July 1785, “Visitations of Greenwich Observatory, 1763 to 1815,” Royal Society, Ms. 600, XIV.d, f. 36.
Table of Contents
Part I: Lord Charles Cavendish
Part II: The Honorable Henry Cavendish
8 Early Researches
17 Last Years
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