The English chemist John Dalton (1766-1844) provided the beginnings of the development of a scientific atomic theory, thus facilitating the development of chemistry as a separate science. His contributions to physics, particularly to meteorology, were also significant.

John Dalton was the youngest of three surviving children of a Quaker handloom weaver. He was born about Sept. 6, 1766 (no exact record exists), in Eaglesfield. Until he was 11, he attended school, then at the age of 12 became a teacher. For about a year he next worked as a farm helper, but at 15 he returned to teaching, privately for the most part, pursuing it as a career for the remainder of his life.

In his work Dalton used relatively simple equipment and has been accused of being "a very coarse experimenter." However, he had a gift for reasoning and for drawing correct conclusions from imperfect experiments. He himself attributed his success primarily...