Sir Humphrey at thirty-seven had immortalized himself. At a public dinner given in his honor at Newcastle, a service of plate worth over twelve thousand dollars was presented to him. After his death this service was given to the Royal Society by his widow, to be sold, and the proceeds applied to the encouragement of science. Emperor Alexander of Russia sent him a splendid silver-gilt vase, with a personal letter; his own sovereign conferred a baronetcy upon him.
When Davy was urged by some friends to take out a patent upon the safety-lamp, and thus make five or ten thousand a year for himself, he said, "I never thought of such a thing: my sole object was to serve the cause of humanity; and if I have succeeded, I am amply rewarded in the gratifying reflection of having done so. I have enough for all my views and purposes; more wealth could not increase either my fame or my happiness. It might undoubtedly enable me to put four horses to my carriage; but what would it avail me to have it said that Sir Humphrey drives his carriage and four?"
He said later of his discovery of the safety-lamp: "I value it more than anything I ever did: it was the result of a great deal of investigation and labor; but if my directions be attended to, it will save the lives of thousands of poor men. I was never more affected than by a written address which I received from the working colliers when I was in the North, thanking me on behalf of themselves and their families for the preservation of their lives."
Sir Humphrey used to say: "Whoever wishes to enjoy peace, and is gifted with great talents, must labor for posterity. In doing this he enjoys all the pleasures of intellectual labor, and all the desire arising from protracted hope. He feels no envy nor jealousy; his mark is too far distant to be seen by short-sighted malevolence, and therefore it is never aimed at.... To raise a chestnut on the mountain, or a palm in the plain, which may afford shade, shelter, and fruit for generations yet unborn, and which, if they have once fixed their roots, require no culture, is better than to raise annual flowers in a garden, which must be watered daily, and in which a cold wind may chill or too ardent a sunshine may dry.... The best faculties of man are employed for futurity: speaking is better than acting, writing is better than speaking."
In the spring of 1818 he took his second continental journey with his wife, going through Austria, Germany, and Italy. Commissioned by his king, he made some researches on Herculaneum manuscripts.
On his return to England he was made President of the Royal Society, the position so ably filled by Sir Isaac Newton. Every Saturday evening, poets, artists, and men of science gathered at his receptions. This office he held for seven years, till his declining health compelled his resignation.
In December, 1821, Davy paid a visit to his old home in Penzance, and saw his mother for the last time before her death. A public dinner was given him by his townsmen, which honor he greatly appreciated. He was no longer the poor lad among them. "Every heart, tongue, and eye were as one to do honor to him who had not only rendered the name of their town famous and imperishable as science itself, but who had added lustre to the intellectual character of their country."
From year to year he continued his experiments. Urged by the commissioners of the navy to remedy the corrosion of copper sheathing on vessels by sea water, he succeeded in rendering the copper negatively electrical by small pieces of tin, zinc, or iron nails. Shells and seaweeds adhered to the non-corroded surface, but the principle of galvanic protection has been applied to various important uses.
In 1824, Sir Humphrey took a journey to Norway, Sweden, and Denmark, visiting Berzelius of Sweden, "one of the great ornaments of the age," he said, and Oersted of Denmark, distinguished for his discovery of electro-magnetism.
Towards the close of 1826, when he was only forty-eight, Davy was attacked by paralysis in the right side, having suffered for a year with numbness and pain in his right arm. During his confinement in his room, he corrected the proof sheets of his "Discourses to the Royal Society," published in January, 1827.