John Dalton was born of a poor Quaker family in the Lake District, a region notorious, even by English standards, for its high rainfall. Meteorology was to remain a lifelong interest. He was largely self-taught. His first book was titled Meteorological Observations and Essays and the last entry in his diary, written the day before he died, was “little rain today.” Dalton was chromatically challenged and his first major paper was an account of “Extraordinary Facts Relating to the Vision of Colours, with Observations.” It constitutes the first systematic study of color-blindness (“Daltonism”), a remarkable achievement for a man who saw geraniums as “sky blue.”

In 1803 Dalton speculated that all atoms of a given element are identical in size and mass and that the relative masses of atoms of different elements can be deduced by an assumed microscopic atom-ratio coupled with macroscopic chemical analysis. In so doing he explained the Law of Constant Composition and rationalized the emerging Law of Multiple Proportions. When in 1808 his ideas were widely circulated in his text A New System of Chemical Philosophy they were met with a mixed reception. Wollaston, Thomson, and Berzelius were (initially at least) enthusiastic converts, while Berthollet and Gay-Lussac were skeptical. For the remainder of his long life, Dalton never wavered in his belief in the literal existence of elementally identical microscopic atoms and fixed-atom ratios, but his contemporaries were less sure and at times disbelieving. It was to be more than fifty years, long after Dalton’s death, before his ideas finally won universal acceptance from chemists. Physicists took a little longer.

During his last 30 years Dalton was decreasingly productive and increasingly celebrated. His elaborate funeral in 1844 proved an embarrassment to his devout Quaker friends.

References
DSB, Vol. III, pp. 537-547.
F. Greenway, John Dalton and the Atom. Ithaca, NY: Cornell, 1966.

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