John Dalton, Thomas Young 37 



months before Gay Lussac, without, however, ever giving 

 the numerical measurements required to prove the law. 

 He was affected by colour-blindness, and first examined that 

 defect scientifically. Dalton died in 1844, being then 

 seventy-eight years old. 



Thomas Young was probably, next to Leonardo da 

 Vinci, the most versatile genius in history. He was 

 descended from a Quaker family of Milverton, Somerset, and 

 at the age of fourteen was acquainted with Latin, Greek, 

 French, Italian, Hebrew, Persian and Arabic. He studied 

 medicine in London, Edinburgh and Gottingen, and subse- 

 quently entered Emmanuel College, Cambridge. In 1799, 

 at the age of twenty-six, he established himself as a physi- 

 cian in London. Subsequently he held for two years the 

 Professorship of Physics at the Royal Institution, but 

 resigned, fearing that his duties might interfere with his 

 medical practice ; during the tenure of his Professorship he 

 delivered many lectures, which were subsequently published, 

 and contain numerous anticipations of later theories. In 

 1804 he was elected Foreign Secretary of the Royal Society, 

 and held that position for twenty-six years. In 1811 

 he became physician to St. George's Hospital, and Super- 

 intendent of the Nautical Almanac. His efforts to decipher 

 Egyptian hieroglyphic inscriptions were among the first that 

 were attended with success. His share in establishing the 

 undulatory theory of light has already been described, and his 

 claims as the founder of physiological optics will be discussed 

 in another chapter (p. 299). Thomas Young was a man 

 of private means, and not dependent on his medical practice 

 for a living. He died in London in the year 1829. To 

 quote Helmholtz : 



" He was one of the most clear-sighted of men who 

 ever lived, but he had the misfortune to be too greatly 

 superior in sagacity to his contemporaries. They gazed 

 at him in astonishment, but could not always follow the 

 bold flights of his intellect." 



Michael Faraday, the son of a working blacksmith, was 

 brought up in humble circumstances, and had but a 

 scanty school education. In 1804, at the age of thirteen, 

 he became an errand boy to a bookseller and stationer in 



