SIR HUMPHRY DAVY (1778-1829), the eminent natural philosopher, was born on the 17th of December 1778, at Penzance, in Cornwall. After receiving there the rudiments of his education, he was in 1792 sent for a year to the grammar school of Truro, then under the direction of the Rev. Dr Cardew. There is little to record of Davy in early life except his retentive memory, facility in versification, and skill in story-telling. At the age of nine he went to live with Mr John Tonkin, who had formerly adopted Davy's mother and her sisters. In 1794 Davy lost his father,.and in the following year he was apprenticed to Mr Borlase, then a surgeon-apothecary, and afterwards a physician in Penzance. During his apprenticeship he spent much of his leisure in a systematic course of self-education. While yet young he had exhibited an inclination for devising experiments, and for examining natural products. At the end of 1797, when in his nineteenth year, he turned his attention to chemistry, and read Lavoisier's and Nicholson's treatises on that subject. His experiments were conducted in the garret of his friend Mr Tonkin, who, alarmed by unexpected explosions would exclaim, "This boy Humphry is incorrigible ! "" Was there ever so idle a dog ! "" He will blow us all into the air ! " One of his investigations at this time was the nature of the air contained in the vesicles of sea-weed. To supply the place of an air-pump in his experiments he had an old French injecting syringe, and this he actually employed in his first scientific paper " On the Nature of Heat and Light," published in 1799. Though Davy's natural talents would not have permitted him to remain long in obscurity, he was in some degree indebted for an early emergence into publicity to the accidental notice of Mr Davies Giddy Gilbert, who, learning that the strange-looking boy, whom he observed hanging over the hatch of Mr Borlase's house, was a son of Davy the carver, and fond of making chemical experiments, sought his acquaintance, and was ever afterwards his steady friend. Another early friend of Davy's was Mr Gregory Watt, who, having visited Penzance in 1797 .for change of air, took lodgings at the house of Mrs Davy. By him and Gilbert he was introduced to the notice of Dr Beddoes, who in the autumn of 1798 engaged him to superintend a pneumatic medical institution, which he had just established at Bristol. Davy was now placed in a sphere where his genius could expand; he was associated with men of education and scientific attainments, and was provided with excellent apparatus ; thus he speedily entered upon that career of discovery which has rendered his name illustrious. He had intended, after the termination of his engagement with Dr Beddoes, to study medicine at Edinburgh, but the all-engrossing interest of his chemical discoveries caused him eventually to abandon this scheme.
In an essay " On Heat, Light, and Respiration," written before he left Cornwall, but published soon after Ms removal to Bristol, in Beddoes's West Country Contributions, Davy endeavoured to prove the immateriality of heat, by showing its generation through the friction of two pieces of ice under an exhausted receiver. His first scientific discovery was that of the existence of silica in the epidermis of the stems of reeds, corn, and grasses. The intoxicating effects of nitrous oxide when respired were discovered by him on April 9, 1799; and in year he published a volume entitled Researches, Chemical and Philosophical, chiefly concerning Nitrous Oxide and its Respiration. Whilst the impression created by this publication was still fresh on the public mind, Davy was recommended to Count Rumford by Mr Underwood and Dr Hope as a suitable person to succeed Dr Garnet as lecturer on chemistry at the Eoyal Institution recently established in London ; and accordingly, on February 16, 1801, he was chosen assistant lecturer to the Institution, and director of the laboratory ; his appointment to the lectureship took place six weeks later. A minute on the records of the Royal Institution shows that he was appointed professor of chemistry on the 31st of May 1802.
The ungainly exterior and peculiar manner of Davy on his first appearance in London prejudiced Rumford and others against him ; when, however, he began to lecture, he won the approbation of all. His ingenuity and happy facility of illustration gained him a high reputation ; his company was courted by the choicest society of the metropolis ; and soon his presence was regarded as indispensable in the soirees of the fashionable world. His style of lecturing was well adapted to command attentionit was animated, clear, and impressive, notwithstanding the naturally inharmonious tones of his voice; his experiments, moreover, were both ingeniously conceived and neatly executed. The young chemist was fortunate in the time in which he commenced his metropolitan career. Experimental chemistry was beginning to be the fashion of the day; and the discovery of the decomposition of chemical substances by voltaic electricity had excited the greatest interest amongst the votaries of science. The liberality of the committee of the Royal Institution supplied to Davy what few private individuals could afforda battery of 400 five-inch plates, and one of 40 plates a foot in diameter. With these were conducted the brilliant investigations which resulted in his discovery of potassium and sodium.
The earliest of Davy's communications to the Royal Society, and the first of his contributions to electro-chemistry, was " An Account of some Galvanic Combinations formed by an arrangement of single Metallic Plates and Fluids," read in June 1801. In all hitherto constructed piles, plates of two metals, or one plate of metal and another of charcoal, and some interposed fluid had been employed. Davy showed in this paper that a battery might be constructed of a single metal and two fluids, provided one of the fluids was capable of causing oxidation on one of the surfaces of the metal. In addition to the duties of his situation in the Royal Institution, to which those of joint editor of the Journal had been added, Davy for ten successive years gave courses of lectures for the Board of Agriculture on the connection between agriculture and chemistry. In 1803 he was admitted a member of the Royal Society, of which he, in January 1807, became the secretary. The most valuable of all his scientific writings are his communications to the Royal Society, scarcely one of which does not announce some new and important fact, or elucidate some principle of experimental philosophy. In February 1803 he read to the society an essay " On Astringent Vegetables, and their Operation in Tanning ;" and in 1805 An Account of some Analytic Experiments on Wavellite," ind a paper " On the Method of Analyzing Stones containing a Fixed Alkali, by Boracic Acid." This method is founded on the strong affinity of that acid for different substances at a high temperature, and on the ease with which borates are decomposed by mineral acids.
In his first Bakerian lecture, delivered to the Royal Society in November 1806, Davy showed that electro-chemical phenomena were explicable by one general law, and illustrated his theory of voltaic action by numerous happily-devised experiments. After pointing out that in all voltaic decompositions acids appeared at the positive and bases at the negative pole, he generalized his results by stating that hydrogen, the alkalies, earths, metals, and certain oxides are attracted by negatively electrified and repelled by positively electrified metallic surfaces, and that oxygen and acids are attracted by positively and repelled by negatively electrified metallic surfaces. He then proceeded to investigate the law of electro-chemical action, and concluded that electro-chemical combinations and decompositions are referable to the law of electric attractions and repulsions, and that both " chemical and electrical attractions are produced by the same cause, acting in the one case on the particles, in the other on the masses." For these researches the French Institute awarded him the prize of 3000 francs offered by the first consul for the experiment most conducive to the progress of science. Davy's discovery of the production of potassium and sodium by the electrical decomposition of their alkalies was made in October 1807, and an account of the new metals was given to the Royal Society on the 19th of November in the second Bakerian lecture. On the 23d of that month a severe fever attacked him, and he was unable to resume his professorial duties at the Royal Institution till March 12, 1808. In the meanwhile barium and calcium, the existence of which had been predicted by Davy, were discovered by Berzelius and Pontin. In 1808 Davy announced to the Royal Society his discovery of magnesium and strontium. Alumina, silica, and zirconia he was unable to decompose, but he showed it to be highly probable that they contained metallic bases. Various opinions as to the nature of the new metals of the alkalies and alkaline earths were at first entertained, some chemists considering them to be compounds of hydrogen with unknown bases. In the third Bakerian lecture, read in December 1808, and its appendix of next spring, Davy adduced conclusive evidence of the elementary nature of potassium ; he discussed also the nature of sulphur, phosphorus, and carbon, and described the preparation of boron, which he then regarded as a metal. The original galvanic batteries used by Davy having become unserviceable through wear, a liberal voluntary subscription among the members of the Royal Institution, in July 1808, put him in possession of a battery of 2000 double plates, with a surface equal to 128,000 square inches. His electro-chemical discoveries had, however, all been made before this new power was provided. The fourth Bakerian lecture, read in November 1809, brings forward proofs that oxymuriatic acid, contrary to Davy's previous supposition, is a simple body, termed by him chlorine (see vol. v. p. 678), and that muriatic acid is a compound of that element and hydrogen.
Davy's reputation had now reached its zenith; and his audience in the theatre of the Royal Institution numbered little less than 1000. At the invitation of the Dublin Society he gave, in November 1810, a course of lectures on electro-chemical science, and in the following year other courses on the elements of chemical philosophy and on geology. For the first of these he received £525, and for the two latter £750; and before he left Dublin, Trinity College conferred upon him the degree of LL.D. On the 8th April 1812 Davy was knighted by the Prince Regent; on the next day he gave his farewell lecture at the Royal Institution ; and on the 11th he married Mrs Appreece, daughter and heiress of Charles Kerr of Kelso, with whom he had a considerable fortune. His usual employments were in great measure suspended during the winter of 1812 in consequence of an injury to an eye, resulting from an explosion of chloride of nitrogen, which he had begun to experiment upon after receiving intelligence of its discovery by Dulong. The first and, as it proved, che only volume of Davy's Elements of Chemical Philosophy appeared in 1812 ; and in 1813 he published his Elements of Agricultural Chemistry, the substance of his lectures delivered to the Board of Agriculture.
Having obtained from the French emperor permission to travel in France, Davy, on October 13, 1813, went thither with his wife and Faraday, the latter in the capacity of " assistant in experiments and writing." Faraday had been engaged on the 1st of March previous to help Davy in the laboratory of the Boyal Institution. On the 29th of October, after a detention of six or seven days at Morlaix, Davy arrived in Paris, where he stayed two months, and began the course of investigations on iodine which enabled him to prove its elementary character. This body had hitherto been regarded as a compound by the French chemists. On the 13th of December Davy was elected a corresponding member of the first class of the Imperial Institute at Paris. From Paris he proceeded, in the end of December, to Montpellier, and thence to Italy. At Genoa and Florence he continued his experiments on iodine; and at the latter place he effected the combustion of the diamond by means of the great lens in the cabinet of natural history, and discovered that, when once ignited, it will continue to burn in pure oxygen. He next proceeded by Rome to Naples, where he collected specimens of the colours used by the ancients in their pictures, which formed the subject of a memoir presented to the Boyal Society. After spending the winter in Italy, he returned to London on April 23, 1815.
The year 1815 is memorable in the history of Davy, as that in which he turned his attention to the frequent occurrence of accidents from explosions of fire-damp in coal-mines. At his request specimens of the gas were sent from Newcastle to London for him to examine. He ascertained that it would not explode when mixed with less than six or more than fourteen times its volume of air, with one-seventh its volume of carbonic acid gas, or with one-sixth its volume of nitrogen; that in tubes one-seventh of an inchin diameter explosive mixturesof air and fire-damp could not be fired; and that metallic tubes prevented explosions better than glass tubes. On November 9, 1815, Davy made known to the Royal Society these results of his experiments ; and before the close of the year he had completed the invention of what has since been known as the Davy safety-lamp (see p. 72 of the present volume). In this a cage of wire-gauze, by its cooling action, prevents the flame from igniting an expulsive atmosphere exterior to the lamp, even though the flame reach as far as the gauze. Of this invaluable aid to the miner the coal-owners of Newcastle and its vicinity were not slow in availing themselves; and on the 11th of October 1817 they testified their appreciation of the boon disinterestedly conferred upon them by Davy, who had taken out no patent for his invention, by presenting him with a suitably inscribed service of plate. In the succeeding year Davy was created a baronet. For his various communications to the Royal Society on the subject of fire-damp, and on the nature of flame, in 1815, 1816, and 1817, he received the Rumford medals.
In 1818 and 1819 he produced four memoirs; " On the Fallacy of the Experiments in which Water is said to have been produced by the Decomposition of Chlorine," "On some Combinations of Phosphorus," " Observations on the Formation of Mists over Lakes and Rivers," and " On Electro-Magnetism." In 1818 he was sent by the British Government to examine the papyri of Herculaneum in the Neapolitan Museum, his remarks on which are contained in a paper in the Philosophical Transactions for 1821. In 1820 Davy returned to England, and on the death of Sir Joseph Banks, in that year, he was elected president of the Royal Society; in this position, however, it cannot be said that he always appeared to advantage, or on every occasion acted in a manner calculated to render himself popular amongst the members. In 1821 he busied himself with electrical experiments, and in 1822 with the investigation of the fluids contained in the cavities of crystals in rocks. In 1823 he read before the Royal Society a paper " On the Application of Liquids formed by the Condensation of Gases as Mechanical Agents." In the same year he investigated the cause of the rapid destruction of the copper sheathing of sea-going ships. It oecurred to him that, as sea-water acts only on positively electrified copper, the sheathing would be protected if he could render it slightly negative. He found that plates of copper having portions of iron or zinc attached remained unchanged after prolonged immersion in sea-water. In consequence of this discovery directions were given by the Government, after some preliminary experiments, to apply plates of iron, or " protectors " as they were called, to several ships of the royal navy ; many merchantmen also were supplied with them. Experience, however, showed that the bottoms of the protected ships soon became extremely foulseaweed and shell-fish accumulating in such quantities as seriously to impede sailing ; so that in June 1825, much to the mortification of the inventor, orders were issued for the removal of the protectors.
In 1826 Davy's health had so far declined that he was with difficulty able to indulge in his favourite sports of angling and shooting ; and on returning to London from Somersetshire he was unable to attend the anniversary dinner of the Royal Society. In January 1827 he published his six anniversary discourses, delivered on awarding the Royal and Copley medals. Early in 1827 he was seized with an apoplectic attack, which rendered his removal to the Continent advisable. After some short stay at Ravenna he removed to Salzburg, whence, on account of the continuance of his illness, he sent in his resignation of the presidency of the Royal Society. At the end of autumn he returned to England, and in the winter he published his Salmonia, a book of some interest, written in imitation of Izaak Walton's Complete Angler.
In 1828 Davy quitted England, and spent most of the summer and autumn at Laybach. In the winter he fixed his residence at Rome, whence he sent to the Royal Society, " Remarks on the Electricity of the Torpedo," written in Illyria in October. This, with the exception of a posthumous work, entitled Consolations in Travel, or the Last Lays of a Philosopher, was the final production of his pen. While at Rome, he was attacked by paralysis, from which he had already suffered. His wife and brother having hastened to his assistance, he left Rome for Geneva, where he died on the 29th of May 1829. His remains were deposited on the 1st of June in the burying-ground outside the walls of that city.
Davy was of a sanguine, somewhat irritable temperament. To all his pursuits he devoted himself with a characteristic enthusiasm and firmness of purpose. His tone of mind, as indicated by his poems, was highly imaginative. "I attend Davy's lectures," said Coleridge, " to increase my stock of metaphors." The power and perspicacity of his intellect is sufficiently attested by his numerous and brilliant discoveries. He was not 21 years of age when he wrote _" It is only by forming theories, and then comparing them with facts, that we can hope to discover the true system of nature." As an experimenter he was remarkably quick; " with Davy," it has been remarked, " rapidity was power." Of the minor observances of etiquette he was careless, and his great frankness of disposition sometimes exposed him to annoyances which the exercise of tact and caution might have obviated. His manner in society, which gave to many the impression of a haughty consciousness of superiority, is ascribed by Dr Paris to " an ungraceful timidity, which he could never conquer."
See Dr J. A. Paris, The Life of Sir Humphry Vary, 1831 ; Dr J. Davy, Works of Sir Humphry Davy, 1839. The former (vol. ii. pp. 450-456) contains a list of Davy's publications. (F. H. B.)