Dalton, John

John (1766-1844), a modest English chemist, known as the author of Dalton's Atomic Theory. For a time Dalton was an instructor in a college at Manchester. During the last forty years of his life he supported himself by taking private pupils at sixty cents an hour. At one time John, being about to revisit his native village, bethought himself that he would bring his Quaker mother a pair of fine silk stockings. He accordingly purchased a pair marked, "Newest fashion"; but his mother's remark, "Thou hast brought me a pair of grand hose, John; but what made thee fancy so light a color? I can never show myself at meeting in them," rather disconcerted him, as to his eyes the hose were of the orthodox drab color. His mother insisted that the stockings were "as red as a cherry." John's brother upheld the "drab" side of the dispute; so the neighbors were called in, and gave their decision that the hose were "varra fine stuff, but uncommon scarlety." Being convinced that he did not see colors well himself, Dalton investigated the question, and found that many people are unable to distinguish all colors; some being deficient as to pink, others as to scarlet, etc. This defect of vision, or color blindness, is often called Daltonism.

Dalton's reputation rests on two principles known as the Atomic Theory:

1. Every element is made up of atoms whose weight is constant. 2. Chemical compounds are formed by the union of the atoms of different elements in the simplest numerical proportions.

Interpreting these principles we say: Silver is an element, and is made up of atoms all alike, each having a weight that never changes. Water is a compound; two atoms of hydrogen unite with an atom of oxygen--never otherwise--to form a molecule of water. A molecule of water then weighs as much as two atoms of hydrogen and one atom of oxygen, never more, never less. The last statement seems selfevident, but it was not so in Dalton's day. Many yet held that heat had weight.

Dalton took some steps in establishing atomic weights. He took the weight of an atom of hydrogen, whatever that might be, as a basis; but he left the work unfinished, and it is incomplete at the present time. In deference to modern scholarship, we should add that there is evidence that even atoms consist of smaller portions of matter.