an outline of his speculations on the subject of the composition of bodies, in which he gave to the world for the first time a Table of Atomic Weights.' In the following year he communicated his views on the theory of definite proportions to Dr. Thomas Thomson, of Glasgow, who at once published an abstract of them; and in 1808 Dalton himself published the first volume of his new system of Chemical Philosophy, in which he placed the Atomic Theory on a firm and clear basis, and established the law of Multiple Proportions. The value of Dalton's researches on this great subject is immense; by the promulgation of his views Chemistry became for the first time a science, and one great law or theory was seen to govern its actions; before it was a series of separate facts, but by this fundamental law and its branches, and by this only, it is preserved as a science.

Dalton's theory incurred much opposition before it was finally accepted by scientific men, and among the unbelievers in it may be mentioned Sir Humphry Davy. The baronet, however, in the year 1826, clearly acknowledged and accurately defined Dalton's discoveries in his anniversary discourse, when he made known that the first award of the Royal Society's Prize, founded by George IV. in the year before, would be given to Mr. John Dalton, "for the development of the chemical theory of Definite Proportions, usually called the Atomic Theory, and for his various other labours and discoveries in physical and chemical science."

During his later life Dalton continued to gain his living as professional chemist, lecturer, and teacher of Chemistry and Mathematics, and contributed to the advancement of science many valuable papers chiefly relating to Chemistry; he was also accustomed in his analytical researches to use the graduated dropping tube, and may be considered as the originator of analysis by volume. Mr. Dalton was present at the first meeting of the British Association held in York in 1831, and continued to feel a lively interest in its prosperity, and to attend the annual meetings as long as his health permitted him. On the occasion of the second meeting at Oxford in 1832, the honorary degree of D.C.L. was conferred upon him, in conjunction with Faraday, Brown the botanist, and Sir David Brewster. In the summer of the following year, at the meeting of the same society in Cambridge, it was announced by Professor Sedgewick, that the King had conferred on Dalton a pension of 1507. per annum, which was increased in 1836 to 3007.; and as his

brother Jonathan died about the same time and left him heir to the paternal estate, he became comparatively wealthy. He, however, still continued working according to his strength, and so late as 1840 published four Essays, entitled, 'On the Phosphates and Arseniates;' 'Microcosmic Salt;' 'Acids, Bases, and Water;' and A New and Easy Method of Analysing Sugar.' In 1837-8 Dalton was attacked by paralysis, which greatly enfeebled him; he, how

ever lived till the year 1844, when a third attack occurred, from which he never recovered, but died shortly afterwards in his seventy-eighth year.

Dr. R. Angus Smith thus describes Dalton's mode of life while living with the family of the Rev. W. Johns, of George Street, Manchester, with whom Dalton continued to reside for twenty-six years: "He rose at about eight o'clock in the morning; if in winter, went with his lantern in his hand to his laboratory, lighted the fire, and came over to breakfast when the family had nearly done. Went to the laboratory and staid till dinner-time, coming in a hurry when it was nearly over, eating moderately, and drinking water only. Went out again and returned about five o'clock to tea, still in a hurry, when the rest were finishing. Again to his laboratory till nine o'clock, when he returned to supper, after which he and Mr. Johns smoked a pipe, and the whole family seems much to have enjoyed this time of conversation and recreation after the busy day.-Life of J. Dalton, by William Charles Henry, M.D., F.R.S., &c. London, 1854.-Life of J. Dalton, by Robert Angus Smith, Ph.D., F.R.S., &c. London, 1856.

SIR HUMPHRY DAVY, BART., LL.D., P.R.S., &c.,

MEMBER OF THE INSTITUTE OF FRANCE, ETC.

Born December 17, 1778. Died May 30, 1829.

This eminent philosopher was born at Penzance, in Cornwall. As a child he was remarkably healthy and strong, displaying at the same time great mental capacity. The first school he ever attended was that of Mr. Bushell, at which reading and writing only were taught. In these rudimentary branches of education he soon made such progress, that he was removed, by the master's advice, to the grammar school kept by the Rev. Mr. Coryton. He was then only six years old. Here Davy received the elements of his education until 1793, when he went to the grammar school of Truro, conducted by the Rev. Mr. Cardew, at which place he continued for about a year.

Both Davy and his family received much assistance from the disinterested friendship of Mr. Tonkin, a respectable medical practitioner at Penzance, who had adopted the mother of Davy and her sisters, under circumstances of deep distress, extending his kindness to all her family, particularly to Humphry.

Soon after leaving Dr. Cardew's school, Davy's father died in 1794;

and in the following year Humphry was apprenticed to Mr. Bingham Borlace, a gentleman at that time practising as surgeon-apothecary in Penzance. While yet very young, Davy had exhibited traces of an ardent and inquisitive mind, displaying also a great predilection for poetry; but from this period he directed his attention more particularly to the study of chemistry and natural philosophy His efforts at attaining an experimental knowledge of the above sciences were, however, greatly retarded by the defects of his apparatus, which was necessarily very limited, and consisted chiefly of phials, wine-glasses, tobacco-pipes, and earthen crucibles. But about this time he had the good fortune to make the acquaintance of Mr. Davies Giddy Gilbert and Mr. Gregory Watt,* by whose instrumentality the subject of our memoir was introduced to Dr. Beddoes, who engaged him to superintend a pneumatic medical institution, which that able but eccentric man had just then established at Clifton, for the purpose of trying the effects of gases upon various diseases. This event took place in 1798, Mr. Borlace readily giving up Davy's indenture, which had not as yet expired. During his residence at Clifton, Davy was placed in a sphere where his genius could expand; he was associated with men engaged in similar pursuits, was provided with suitable apparatus, and enabled to speedily enter upon that brilliant career of discovery which has rendered his name illustrious among philosophers.

Soon after he had removed to the neighbourhood of Bristol, Davy's first published paper, on 'Heat, Light, and Respiration,' appeared in 'Beddoes' West Country Contributions.' His earliest scientific discovery was the detection of siliceous earth in the epidermis of canes, reeds, and grasses.

About the same period, he began to investigate the properties of gases, and discovered the respirability of nitrous oxide, giving in a letter to his friend Mr. Davies Gilbert (dated April 16, 1799), the first intimation of the intoxicating qualities of that gas. Shortly afterwards he examined its properties more accurately, administering it to various individuals, and published an account of his discoveries in a volume entitled 'Researches Chemical and Philosophical chiefly concerning Nitrous Oxide and its Respiration.' While the favourable impression from this publication was still fresh on the public mind, the establishment of the Royal Institution, under the auspices of Count Rumford, had taken place, and a lecturer of talent was wanting, to fill the chemical chair. Through the recommendation of Dr. Hope of Edinburgh, with whom he had become acquainted Davy received the appointment, and became lecturer to the institution and director of the laboratory.

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

*Youngest son of James Watt.

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.* 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 7501.,-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

Davy also reduced by voltaic electricity alumina, but aluminium was first obtained in a perfectly separate state by Wöhler in 1827.