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 DAYY 719 the vesicles of the common seaweeds thrown upon the shore, and he demonstrated that the marine plants act upon the air in precisely the same way as the terrestrial, by decomposing carbonic acid under the influence of the sun's rays, to obtain the carbon necessary for their growth, and the oxygen for their respiration. In 1798 he was invited by Dr. Beddoes to be- come assistant in his pneumatic institution at Clifton, in which pulmonary diseases were treated by the inhalation of different gases; and early in October he went there. He made his experiments on the protoxide of nitrogen (laughing gas) in 1799, and published the re- sults in 1800; he also experimented with car- buretted hydrogen, carbonic acid, and nitro- gen, thereby seriously injuring his health. About the same time he had taken up the subject of galvanism, which afterward led to some of his greatest discoveries in decomposing the alkalies and alkaline earths. The pneu- matic institution soon became very popular under his management, and some of the most obstinate diseases were benefited by the new remedies; the nitrous oxide was found very beneficial in many cases of palsy. The royal institution had just been founded, with the in- tention of diffusing a knowledge of science in its application to the common purposes of life ; Davy accepted the invitation to become lecturer on chemistry, took up his abode in London in March, 1801, and was formally ap- pointed professor in May, 1802. His lectures at once became exceedingly popular; his youth, simple manners, and eloquence, his knowl- edge of his subject, and his brilliant experi- ments excited the attention of members of the highest ranks in London, and his society was courted by all. During the 11|- years that he spent in the rooms of the royal insti- tution, his bachelor apartments were furnished in the simplest manner ; in the adjoining labo- ratory he spent most of his time, preparing for his lectures, and conducting his investigations. His observations on tanning were published in the "Philosophical Transactions" for 1803; and his lectures before the board of agricul- ture, which were delivered till 1813, were published under the title of " Elements of Agri- cultural Chemistry," a work which has passed through many editions, and has been translated into almost every European language. His re- searches in electro-chemical science had been commenced at Clifton, and the results are pub- lished in the " Philosophical Transactions " from 1808 to 1812, and in the early "Bakerian Lectures " of 1806-'7. The base potassium was discovered Oct. 6, 1807, and sodium a few days after, by decomposing moistened potash and soda by several voltaic batteries ; his delight when he saw the globules of potassium appear and take fire as they entered the air was so great that it was some time before he could compose himself sufficiently to continue the experiment. His mental labor and excite- ment over his discoveries threw him into a 251 VOL. v. 46 typhoid condition, which threatened his life for several weeks. On his recovery he experi- mented with a battery of 2,000 plates, and showed the simple nature of chlorine, sulphur, and phosphorus, and many other important facts. In 1803 he was elected a fellow, and in 1807 one of the secretaries of the royal so- ciety, which appoinment he held for five suc- cessive years. The medical profession seerns now to have been resumed for a short time ; but the claims of science had too great an at- traction, and he gave up medicine, as he had previously declined an invitation to enter the church. So great was his reputation as a lec- turer that he was invited to deliver courses before the Dublin society in 1810 and 1811, for which he received 1,200, and was made doc- tor of civil law by Trinity college. He was knighted in April, 1812, by the prince regent, and in the same month married Mrs. Apreece, a widow, who brought him a considerable for- tune ; he was created a baronet in 1818. In the autumn of 1813, by express permission of the French government, granted on account of his scientific reputation, he visited the. continent during the war, in company with Mr. Faraday " as his assistant in experiments and in wri- ting." While in Paris, where he spent two months, he became acquainted with Cuvier, Laplace, Gay-Lussac, Humboldt, and Vauque- lin ; and during this brief period he discovered that iodine is a simple substance, analogous in its chemical relations to chlorine. He remain- ed on the continent until the spring of 1815, visiting the south of France, Italy, and Switz- erland, devoting special attention to the vol- canic regions, and pursuing his chemical re- searches on colors, the iodine compounds, and oxymuriate salts, which were published in the "Philosophical Transactions" for 1815. His next discovery placed him among the greatest benefactors of his race. In May, 1812, a ter- rific explosion of gas took place in the Felling colliery near Newcastle, causing the death of 92 men ; and after many other such disasters, a committee of proprietors of mines waited upon Davy to see if he could devise any way of preventing similar accidents. He began by analyzing the gas, and ascertaining in what proportions its mixture with air rendered it most explosive, and the degree of heat neces- sary to ignite it ; from observing that the com- bustion was not communicated through tubes of small dimensions, he gradually reduced the length of the tubes till he found that a simple metallic gauze, with apertures not exceeding ^j of an inch square, was sufficient to prevent the burning gas inside from igniting the great explosive mass on the outside ; he accordingly covered the lamps with a wire tissue, perme- able to air and light, but not to flame. This simple contrivance constituted the miner's safe- ty lamp, and has saved the lives of thousands; the dangerous gas may burn within the gauze, and thus give timely warning, and may at last extinguish the lamp, but a suspended platina