It is a singular fact, that although Davy's attention had never been confined to his favourite science, for he had studied general literature as well as poetry, yet he was of so uncouth an exterior and manners, notwithstanding an exceedingly handsome and expressive countenance, that Count Rumford, a leading director of the Institution, on seeing him for the first time, expressed no little disappointment, even regretting the part he had taken in promoting the engagement. But these feelings were of short duration. Davy was soon sufficiently humanized, and even refined, to appear before a London and a fashionable audience of both sexes with great advantage, and by his ingenuity, and happy facility of illustration, he rendered his lectures so popular, that at the early age of twenty-two, he found his company courted by the choicest society of the metropolis. An anecdote is told illustrative of his popularity, even among the more humble classes. While passing through the streets one fine night, he observed a man showing the moon through a telescope to the surrounding bystanders; Davy stopped to have a look, and having satisfied his curiosity, tendered a penny to the exhibitor. The man had, however, in the meanwhile, learnt the name of his customer, and exclaimed, with an important air, that he could not think of taking money from a 'brother philosopher.' Davy's style of lecturing was animated, clear and impressive, notwithstanding the naturally inharmonious tones of his voice; whilst the ingenuity of his happily devised experiments, the neatness of their execution, and above all the ingenious enthusiasm which he displayed for his subject, fixed and arrested the attention of his hearers.
At this time, experimental chemistry began to be the fashion of the day. Voltaic electricity had just been found to possess extraordinary powers in effecting the decomposition of chemical compounds; and by the liberality of the Royal Institution, Davy was put in possession of a battery consisting of 400 5-inch plates, and one of 40 plates, 1-foot in diameter, with which batteries his early and most brilliant investigations were conducted.
In 1801 he made his first important discovery, which was communicated to the Royal Society under the title 'An Account of some Galvanic Combinations formed by an Arrangement of Single Metallic Plates and Fluids,' read in June of the same year. In this paper, he showed that the usual galvanic phenomena might be energetically exhibited by a single metallic plate, and two strata of different fluids; or that a battery might be constructed of one metal and two fluids, provided one of the fluids was capable of oxidizing the surface of the metal. In the following year to this, Davy was appointed professor to the Board of Agriculture, and in 1803 was admitted a member of the Royal Society, of which he became first the secretary, and ultimately the president.
To the 'Philosophical Transactions' of this society he continued to contribute papers on different branches of experimental philosophy; and it is on these papers that his claims to celebrity almost entirely rest. From 1802 to 1805, Davy published several minor papers; but in the following year appeared his first Bakerian lecture, read to the Royal Society in November, 1806, in which he detailed the phenomena of electro-chemical decomposition, and laid down its laws; while in his second lecture, read in the November following, he announced the successful application of these principles, and the discovery of the metallic bases of the fixed alkalies, witnessed by the production of two new metals, which he named potassium and sodium.[18] This splendid discovery was fully confirmed by Guy Lussac and Thenard, who, in the following year, succeeded in decomposing potash by iron filings, in a red-hot gun barrel. From 1808 to 1810, Davy gave three more lectures, in which he announced the results of his further chemical investigations. It may be interesting to remark that the original batteries of the institution were so worn during the course of his experiments, as to be unserviceable; a liberal voluntary subscription, however, amongst the members, in July 1808, put him in possession of the most powerful voltaic battery ever constructed, consisting of 2000 double plates, with a surface equal to 128,000 square inches. The results produced by this tremendous power did not, however, add to science one new fact of any importance. All Davy's great voltaic discoveries were made before it was in use, and it only served to show the phenomena of galvanism with greater brilliancy.
Mr. Davy's reputation was now at its height, and he was invited by the Dublin Society to give a course of lectures on electro-chemical science. For these lectures, which were commenced on the 8th, and concluded on the 29th of November, 1810, he received 500 guineas. In the following year he was invited to give two more courses, on the Elements of Chemical Philosophy, and on Geology, for which he received 750l.,—the Provost and Fellows of Trinity College also conferring on him the degree of LL.D. In 1812, Davy dissolved his connection with the Royal Institution, by giving a farewell lecture on the 9th of April; on the preceding day he had received the honour of knighthood from the hands of the Prince Regent, and on the 11th of the same month was married to Mrs. Apreece, daughter and heiress of Charles Kerr, of Kelso, and the possessor of an ample fortune. During the next two or three years, Sir Humphry communicated several papers to the Royal Society, but they contained little of importance to science.
Whilst experimenting, in the latter part of 1812, upon azote and chlorine, he was severely wounded in the eye by the explosion of these substances; and it is a strong proof of his energy, that when his eye was sufficiently recovered, he renewed his experiments upon the same bodies, and was again wounded in the head and hands, but this time slightly, as he had taken the precaution of defending his face by a plate of glass.
In the autumn of 1813 he obtained the permission of Napoleon to travel in France, whither he proceeded, accompanied by his lady and Mr. Faraday. From France, Davy proceeded to Italy, where he spent the winter, returning to London on the 23rd of April, 1814. During his stay in Italy, he collected specimens of the colours used by the ancients in their pictures. This formed the subject of a memoir to the Royal Society, the most interesting part of the paper being the announcement that the fine blues of the ancients were formed of silex, soda, and copper, and that they may be exactly imitated by strongly heating together, for the space of two hours, three parts of copper filings, fifteen of carbonate of soda, and twenty of powdered flint.
In the year 1816, Davy turned his attention to a method of preventing the dreadful accidents in coal mines, from explosions of the fire-damp. After considerable investigation, he found that this gas would not explode when mixed with less than six times or more than fourteen times its volume of atmospheric air; and in the course of experiments made for the purpose of ascertaining how the inflammation takes place, he was surprised to observe that flames will not pass through tubes of a certain length or smallness of bore. He then found that if the length was diminished, and the bore also reduced, that flames still would not pass; and further, that the length of the tubes might safely be diminished to hardly anything, provided their bore was proportionably lessened. Working from these principles, he proposed several kinds of lamps, but all were finally superseded by the simple one known as the Davy safety-lamp, in which a small oil light is covered by a cylinder of wire gauze, the small apertures[19] of which flame will not pass through, and the explosion is thus prevented from extending outside the wire gauze. The introduction of this beautiful invention, although freely given to the public, was for a time violently opposed by prejudice and passion. Experience, however, showed the comparative safety which the miners who used it possessed, and the coal-owners of Newcastle and the vicinity presented Davy with a superb service of plate, as some recognition of the important benefit he had conferred on them.
During the later years of Sir Humphry Davy's life, various communications appeared from him to the Royal Society, none, however, presenting any very remarkable features. In November, 1820, a few months after the death of Sir Joseph Banks, he was elected president of the above society. In 1823 he repeated the interesting experiment of Mr. Faraday, as to the condensation of gases by mechanical pressure, and succeeded in converting sulphurous acid and prussic acid gases into liquids, by heating them in strong sealed tubes. During the same year he investigated the causes of the rapid decay of copper sheathing on ships, and attributing this to electro-chemical action, succeeded in preventing it, by attaching plates of iron or zinc to the copper. This, however, on being tried practically, introduced the unlooked for evil, of excessive fouling of the bottoms of ships so protected, which became liable to marine deposits in an equal manner with wooden bottoms. Davy's plan was thus rendered utterly useless, much to his mortification.
During the later portion of his life, Sir Humphry was in very infirm health, and in 1828 he determined to go abroad. Proceeding into Italy, he fixed his residence at Rome, whence he sent his last communication to the Royal Society, viz., 'Remarks on the Electricity of the Torpedo.' The chief peculiarity of this paper was the discovery that the electricity of this curious creature had no effect on the most delicate galvanometer. While staying at Rome, Sir Humphry was seized with a paralytic attack, which greatly alarmed his friends. Shortly afterwards he left Rome for Geneva, on reaching which city an attack of apoplexy seized him during the night, which terminated fatally. The funeral took place on the 1st of June, 1829, with all the honour and respect the inhabitants of Geneva could testify. His remains were deposited in the burying-ground of the city, without the walls, the spot being marked by a simple monument, with a Latin inscription, erected by Lady Davy.—Life of Sir H. Davy, by his brother, John Davy, M.D., F.R.S. London, 1839.—Memoir by Dr. Thomas Trail, Encyclopædia Britannica.—Weld's History of the Royal Society, with Memoirs of the Presidents. London, 1848.—Brougham's Lives of Philosophers. London and Glasgow, 1855.