John Dalton (1766-1844)
Dalton achieved fame as a chemist.
From 1787 until his death he kept a diary of weather observations and gave lectures on this subject to the Manchester Literary and Philosophical Society. In 1793 he took up a post in Manchester teaching mathematics and natural philosophy (science). He investigated how the volume of a gas varies with temperature, concluding that all gases have the same coefficient of thermal expansion. In 1801 he formulated his law of partial pressures.
Following this, in 1803, his work on the solubility of gases led him to formulate his atomic theory. Dalton's theory defined an atom as the smallest part of a substance that can take part in a chemical reaction, and assumes that elements are made of atoms, which combine in definite proportions.
Dalton's work laid the foundations for modern atomic theory. He also gave the first detailed description of colour blindness, a condition he shared with his brother. He died in Manchester, 27 July 1844.