John Dalton

John Dalton was an English chemist and physicist whose 1808 book A New System of Chemical Philosophy proposed that each element is made of identical, indivisible atoms of a characteristic weight, that compounds form when atoms of different elements combine in small whole-number ratios, and that chemical reactions rearrange atoms without creating or destroying them. The theory gave the existing law of multiple proportions a physical explanation and let chemists calculate relative atomic weights for the first time. Dalton was colorblind and published one of the first scientific descriptions of the condition in 1794, drawing on his own vision; it is still sometimes called Daltonism. He never married, lived most of his life in Manchester, and died in 1844.