# Biographies of Scientific Men/Cavendish

CAVENDISH
1731-1810
TWO years before the birth of Priestley, and in the reign of George II., there was born at Nice, on 10th October 1731, a son to Lord Charles Cavendish, and a nephew of the third Duke of Devonshire. The family is an old one, and traces its descent to Sir John Cavendish, Lord Chief Justice in the reign of Edward III., and to Robert de Gernon a compatriot of the Norman Conqueror; and the ﬁrst peer was son to William Cavendish, usher to Cardinal Wolsey. The mother of the Hon. Henry Cavendish died when he was two years old, and of his boyhood days nothing is known. At the age of eighteen he went to Cambridge, remaining at Peterhouse for four years, but did not take his degree. This representative of a noble house was a recluse, cold, passionless, selfish, reticent, a misogynist, a hater of noise and bustle, a man of few words, a millionaire, and a devotee to science. "There was nothing earnest, enthusiastic, heroic, or chivalrous in the nature of Cavendish, and as little was there anything mean, grovelling, or ignoble. All that needed for its ​apprehension more than pure intellect, or required the exercise of fancy, imagination, affection or faith, was distasteful to Cavendish. An intellectual head thinking, a pair of wonderfully acute eyes observing, and a pair of very skilful hands experimenting, or recording, are all that I realize in reading his memorials," wrote his biographer sixty years ago.
Cavendish was a profound chemist, mathematician, astronomer, electrician, geologist, and meteorologist; and for fifty years he constantly published important papers in the Philosophical Transactions of the Royal Society. Priestley and Cavendish were contemporaries. The work of the former was brilliant and quick; that of the latter was slow and thorough. Although Cavendish wrote much, he had an innate dislike to publicity. He published few papers, destroyed many, and therefore some of his brilliant researches were lost to science. His dread of popularity, want of laudable ambition, lack of enthusiasm, and morbid shyness compelled him to refrain from publishing many important scientific papers. Will there ever be an adequate life of Cavendish? Never. This remarkable man of solitary habits destroyed more papers than he ever published. No doubt the world lost much, for as Sir Humphry Davy said of Cavendish's researches, "they were all of a finished nature, and though many of them were performed in the very infancy of chemical science, yet their accuracy and their beauty have remained unimpaired."
​Cavendish's residences were in Gower Street and Dean Street, Soho, but his favourite home was Cavendish House, Clapham. In the last-mentioned residence (which was demolished in 1905) most of the rooms were converted into laboratories, workshops, and observatories. The author visited Cavendish House and grounds on 9th August 1905, and took several photographs. The house was situated on the south side of Clapham Common, and within its walls one of the most remarkable feats of science was accomplished. Just under the vane (centre window of the second storey) was a small room in which Cavendish weighed the earth.
In 1798 he computed its mean density by comparing the force of terrestrial attraction with that of the attraction of something of known magnitude and density. This done, an approximation of the weight of the earth became possible. The mean of twenty-three experiments was that the earth weighed 5·45 times that of a globe of water of equal size—the accepted figure now being 5·50. This and a vast amount of work was performed within the walls of Cavendish House, which stood in nine acres of beautifully timbered land; and here one of England's greatest chemists "buried his science and his wealth in solitude."
It was in this house that exact quantitative work on electricity received a great impetus by the researches of Cavendish. In 1771 he published important ​contributions to electrical theory, amongst them being an ingenious null method by which the law of inverse squares was proved to a high degree of accuracy. He also was the first to make quantitative measurements in electrical resistance—one of his experiments gave the specific resistance of water as four hundred million times that of iron.
Cavendish, about 1775, showed that the capacity for a condenser depends not only on its geometrical shape and dimensions, but also on the dielectric employed, and that the capacity is greater when solid dielectrics take the place of air. Cavendish's results were not published at the time, and only verbally did his contemporaries know anything of his work. Sixty-two years afterwards Faraday investigated the phenomena of condensers.
In his wildest dreams, however, Cavendish cannot have anticipated that in less than a century after his death a service of electric cars would be passing Cavendish House. Most likely the recluse would not have liked the prospect if the idea had occurred to him, as he hated "noise and bustle."
Cavendish lived a life of perfect retirement in Cavendish House. Society was a bore to him; he received no strangers, and held no communication with female servants. His horror of women was extreme. He ordered his dinner by leaving a note on the hall table every day; and orders were given that no female servant ​was to show herself on pain of instant dismissal. He had no friends—real friends—only scientific acquaintances, and these had to be very careful how they spoke to him, or he would become perfectly silent and leave their presence. It is said of this remarkable man—one of the most eccentric characters of his time—that he uttered fewer words in the course of his long life than even a Trappist monk.
In Cavendish House he discovered the composition of water, and made other momentous scientific discoveries. Despite his immense wealth (he was the richest man in London in his day), he lived in the simplest fashion, reserving only one or two rooms for domestic purposes.
Cavendish was tall and thin, with wizened features. He wore old-fashioned clothes—even for the times in which he lived—and a knocker-tailed periwig. He would never sit for his portrait. Our illustration is a copy of a drawing made surreptitiously by a contemporaneous artist.
hon. henry cavendish and cavendish house, clapham
Many are the stories of this eccentric individual. A few, however, must suffice. Ingenhousz, a distinguished scientist, entered upon a complimentary harangue, saying he had only come to England for the purpose of seeing the great Cavendish—so profound and so universally celebrated. Cavendish became speechless, nervous agitation seized him, and, overwhelmed with confusion, made a hasty retreat from the room, and on reaching his carriage was driven home.
On one occasion three or four friends (or rather acquaintances) being invited to dine with him, he was asked what he would like for dinner. He replied, "a ​leg of mutton." "But," said the servant, "that will not be enough for five." "Then get two legs," was his reply.
Another story is told that Cavendish's banking account had accumulated to the extent of £80,000, and when his banker asked whether it should be invested, he replied, "Do what you like with it, but trouble me no more about it, or I will place my account elsewhere."
Although a marvellously accurate worker, Cavendish was not free from bias. Like Priestley, he was a phlogistian, and his chemical papers are written in the jargon of the school of Stahl. In 1766 he published his first paper, which was entitled "On Factitious Airs"; but before this time he wrote two papers: "Experiments on Arsenic" and "Experiments on Heat," which, however, due to his horror of publicity, were not published until after his death. In 1788 Cavendish published his famous paper, "Experiments on Air," in which he says: "As far as the experiments hitherto published extend, we scarcely know more of the nature of the phlogisticated part (nitrogen) of our atmosphere, than that it is not diminished by lime-water, caustic alkalis, or nitrous air; that it is unfit to support fire, or maintain life in animals; and that its specific gravity is not much less than that of common air; so that though the nitrous acid by being united to phlogiston is converted into air possessed of these properties, and, consequently, though it was reasonable to suppose that part at least of the phlogisticated air of the atmosphere ​consists of this acid united to phlogiston, yet it might fairly be doubted whether the whole is of this kind, or whether there are not in reality many different substances compounded together by us under the name of phlogisticated air. I therefore made an experiment to determine whether the whole of a given portion of the phlogisticated air of the atmosphere could be reduced to nitrous acid, or whether there was not a part of a different nature from the rest which would refuse to undergo that change. . . . If there is any part of the phlogisticated air of our atmosphere which differs from the rest, and cannot be reduced to nitrous acid, we may safely conclude that it is not more than 1/120 part of the whole." This is of vast importance, if we bear in mind the discovery of argon as a constituent of the atmosphere by Rayleigh and Ramsay in 1894, and the later work of Ramsay and Travers on krypton, neon, and metargon.
Although Cavendish's work on atmospheric gases was of great importance, it led him to a still more famous discovery, namely, the composition of water in 1781; and in his paper of 1784 he says: "By the experiments with the globe it appeared that when inflammable air (hydrogen) and common air are exploded in a proper proportion, almost all the inflammable air, and nearly one-fifth of the common air, lose their elasticity and are condensed into dew. And by this experiment it appears that this dew is plain water, and, consequently, that almost all the inflammable air, and ​about one-fifth of the common air, are turned into pure water." He further showed that when dephlogisticated air (oxygen) and inflammable air (hydrogen) were exploded together, pure water was the result.
Although he proved the composition of water, it does not appear that he viewed it as a chemical compound of the two gases. His phlogistic ideas biased even his clear mind to such an extent that, after the overthrow of the phlogistic doctrine by the work of Lavoisier, he withdrew from any active part in scientific research.
In 1783, in a letter to Black, James Watt expressed the opinion that "water is composed of dephlogisticated and inflammable airs." A long and bitter controversy raged about the discovery, the priority of which was claimed for Watt. It is now, however, universally ascribed to Cavendish.
Although nitric acid was known to Geber—the eighth-century alchemist—Cavendish proved (1784-85) the exact composition and mode of formation of this acid. He was remarkable for the accuracy and precision of his experimental discoveries; but any attempt to draw him into conversation was useless. "The way to talk to Cavendish," said Wollaston, "is never to look at him, but to talk as it were into vacancy, and then it is not unlikely you may set him going."
In 1766 Cavendish discovered inflammable air (the hydrogen of to-day), producing it by the action of dilute ​acids on zinc or iron, and he describes its properties in the first part of his paper "On Factitious Airs." In the same paper he discussed the properties of fixed air (carbon dioxide), and proved that fixed air and the air produced during fermentation were the same.
Early in his career Cavendish made researches into the properties of heat—discoveries in regard to specific and latent heat which anticipated those subsequently made and published by Black—but it is said suppressed them that he might not enter into rivalry with the learned Scotch professor. One pauses in wonder to contemplate a man who could give away fame in so easy-going a fashion, and, moreover, was willing to do so.
The life of Cavendish presents a deeply interesting, but difficult, problem for the student of psychology.
His immense library was available to all his scientific acquaintances on condition that they did not disturb the owner; and on one occasion he was induced to allow a fellow-worker of small means to reside in his London library in order to catalogue and rearrange it. After leaving London, the poor fellow was not in the best of health, and was indifferently provided for. It was suggested to Cavendish that he was deserving of "a little annuity for life." "Well, well, well, a cheque for ten thousand pounds, would that do?" asked Cavendish; and a cheque for that amount was accordingly written. This was the only generous act in his long life of eighty years; and he ​died possessed of more than £1,157,000. He was a selfish cynic, ignorant of humour and of pathos, devoid of all human sympathy; love, joy, sorrow, and pity were absent in his nature; he had a leichenbittermiene; and, with the exception of the highest intelligence, his life was a blank. With his vast wealth he did no good, not even to science, for he left none to further the aims of his favourite pursuits. Cavendish lived alone, worked alone, and died alone!
When near his end, he called his servant to his bedside, and said: "Mind what I say—I am going to die. When I am dead, but not till then, go to Lord George Cavendish and tell him—go!" He ordered the servant from the room, as he wished to be left alone. Shortly afterwards it was found that Cavendish had "joined the majority"—"abiit ad plures." He died in London on 24th February 1810, and lies buried in the family vault in All Saint's Church, Derby.
It has been said of Cavendish that "in extent of acquirements, and in profundity of learning, he was unsurpassed by any of his contemporaries."
Who are the great? Those who have boldly ventured to explore Unbounded seas, and lands unknown before— Soared on the wings of Science, wide and far, Measured the sun, and weighed each distant star, Pierced the dark depths of ocean and of earth, And brought uncounted wonders into birth;
And given new beauty to the human form; Wakened the voice of reason, and unfurled The page of truthful knowledge to the world. They who have toiled and studied for mankind, Aroused the slumbering virtues of the mind, Taught us a thousand blessings to create— These are the nobly great!
Among Cavendish's other investigations may be mentioned his work on the thermometer and temperatures; he proved that heat was a mode of motion, thereby refuting the material theory. The origin of the "fur" in a tea-kettle was first noted by Cavendish, and the fact that hard waters could be rendered soft by the addition of lime was demonstrated by him. He also proved, by quantitative experiments, that fixed air (carbon dioxide) was heavier than common air, and performed other work on gases. He invented the eudiometer; but his two crowning discoveries were the determination of the composition of water, and the weight of the earth.
Although Cavendish retained the terminology of the phlogistic doctrine, he practically admitted the essential point of the nouvelle chimie of Lavoisier, namely, that calces are compounds of metals and dephlogisticated air (oxygen). He was elected an F.R.S. in 1764, and in 1801 one of the eight foreign associates of the French Académie des Sciences.
Of posthumous honours, the seventh Duke of Devonshire, himself a distinguished mathematician, erected and ​endowed the world-famed Cavendish Laboratory at Cambridge as a memorial to his illustrious ancestor.
Concerning the author's photographs of the now demolished Cavendish House, the following quotations of letters received by him may not be out of place:—
Professor J. J. Thomson, LL.D., F.R.S., Director of the Cavendish Laboratory, says: "I am greatly indebted to you for the very interesting photographs of the house in which Cavendish lived and worked. I shall have them framed and put near a picture of Cavendish we have in the laboratory." Sir Oliver Lodge writes that "they are an interesting reminiscence of a great man." Lord Rayleigh writes: "He was a queer creature in many ways, but I have always had the greatest admiration for his scientific work." The Hon. R. J. Strutt, F.R.S., writes that "the photographs are of much historical, scientific interest, and as a great admirer of the wonderful precision of Cavendish's work, I am very pleased to have them."
Such are the opinions of some of the foremost living scientists concerning the work of Cavendish.
His fortune, already alluded to, went to his cousin, an ancestor of the ninth and present Duke of Devonshire.
In conclusion, Galileo suffered for saying that the earth revolved round the sun, but what would the Roman hierarchy have done to Cavendish for daring to weigh it? •••••••
​If the Church punishes in one age, it condones in another. Pope Leo XIII. removed from the Index Librorum Prohibitorum the two works of Galileo—De Revolutionibus and The Dialogues on Motion, one of which asserted that "the earth was not the centre of the universe, nor immovable, but that it moves even with diurnal motion," this being considered "a proposition absurd and false in philosophy and erroneous in faith." Sentence was pronounced on 22nd June 1633, so that the master's great works have been forbidden to the faithful two hundred and sixty-eight years! The whole proceeding was strange and irregular. Pope Urban VIII. did not sign the condemnation. Copernicus (1473-1543), a priest, taught the same doctrine; and Kepler (1571-1630), by his planetary laws, had founded the new astronomy. Galileo (1564-1642) only confirmed what they had taught. The year that he died Newton was born, in a land where no Inquisition could stay inquiry. Moreover, in England the Copernican theory created no religious alarm! . . . More imperishable than the marble monument in Santa Croce are the two books liberated from the Index. . . . Cavendish performed a monumental feat in weighing the earth, although one which would have brought him before the members of the Inquisition had he lived in Italy or Spain in the sixteenth century!