He lectured before the Dublin Society in 1810, and again in the following year; on the occasion of his second visit receiving the degree of LL.D. from Trinity College. He was knighted in the spring of 1812, and was married to a handsome, intellectual, and wealthy lady. He was appointed Honorary Professor of Chemistry at the Royal Institution. His new independence gave him full liberty to pursue his scientific interests. Toward the close of 1812 he writes to Lady Davy:—
"Yesterday I began some new experiments to which a very interesting discovery and a slight accident put an end. I made use of a compound more powerful than gunpowder destined perhaps at some time to change the nature of war and influence the state of society. An explosion took place which has done me no other harm than that of preventing me from working this day and the effects of which will be gone to-morrow and which I should not mention at all, except that you may hear some foolish exaggerated account of it, for it really is not worth mentioning...." The compound on the investigation of which he was then engaged is now known as the trichloride of nitrogen.
In the autumn of 1813 Sir Humphry and Lady Davy, accompanied by Michael Faraday, who on Davy's recommendation had in the spring of the same year received a post at the Royal Institution, set out, in spite of the continuance of the war, on a Continental tour. At Paris Sir Humphry was welcomed by the French scientists with every mark of distinction. A substance which had been found in the ashes of seaweed two years previously, by a soap-boiler and manufacturer of saltpeter, was submitted to Davy for chemical examination. Until Davy's arrival in Paris little had been done to determine its real character. On December 6 Gay-Lussac presented a brief report on the new substance, which he named iode and considered analogous to chlorine. Davy, working with almost incredible rapidity in the presence of his rivals, was able a week later to sketch the chief characters of this new element, now known by the name he chose for it—iodine.
We have passed over his investigation of boracic acid, ammonium nitrate, and other compounds; we can merely mention in passing his later studies of the diamond and other forms of carbon, of the chemical constituents of the pigments used by the ancients, his investigation of the torpedo fish, and his anticipation of the arc light.
It seems fitting that Sir Humphry Davy should be popularly remembered for his invention of the miner's safety-lamp. At the beginning of the nineteenth century the development of the iron industry, the increasing use of the steam engine and of machinery in general led to great activity and enterprise in the working of the coal mines. Colliery explosions of fire-damp (marsh gas) became alarmingly frequent, especially in the north of England. The mine-owners in some cases sought to suppress the news of fatalities. A society, however, was formed to protect the miners from injury through gas explosions, and Davy was asked for advice. On his return from the Continent in 1815 he applied himself energetically to the matter. He visited the mines and analyzed the gas. He found that fire-damp explodes only at high temperature, and that the flame of this explosive mixture will not pass through small apertures. A miner's lamp was therefore constructed with wire gauze about the flame to admit air for combustion. The fire-damp entering the gauze burned quietly inside, but could not carry a high enough temperature through the gauze to explode the large quantity outside. To one of the members of the philanthropic society which had appealed to him Davy wrote: "I have never received so much pleasure from the result of any of my chemical labours; for I trust the cause of humanity will gain something by it."
Davy was elected President of the Royal Society in 1820, and retained that dignity till he felt compelled by ill health to relinquish it in 1827. "It was his wish," says his brother, "to have seen the Royal Society an efficient establishment for all the great practical purposes of science, similar to the college contemplated by Lord Bacon, and sketched in his New Atlantis; having subordinate to it the Royal Observatory at Greenwich for astronomy; the British Museum, for natural history, in its most extensive acceptation."
Sir Humphry Davy, after a life crowded with splendid achievements, died at Geneva in 1829 with many of his noblest dreams unfulfilled. Fortunately in Michael Faraday, who is sometimes referred to as the greatest of his discoveries, he had a successor who was fully adequate to the task of furthering the various investigations that his genius had set on foot, and who, to the majority of men of mature mind, is no less personally interesting than the Cornish scientist, poet, and philosopher.
REFERENCES
John Davy, Works of Sir Humphry Davy.
John Davy, Fragmentary Remains, literary and scientific, of Sir Humphry Davy, Bart.