DALTON, JOHN (1766-1844), English chemist and physi cist, was born about Sept. 6, 1766, at Eaglesfield, near Cocker mouth in Cumberland. His father, Joseph Dalton, was a weaver in poor circumstances, who belonged to the Society of Friends. John received his early education from his father and from John Fletcher, teacher of the Quakers' school at Eaglesfield, on whose retirement in 1778 he himself started teaching. But he earned only about five shillings a week, and after two years he took to farm work. He received some help in his mathematical studies from a distant relative, Elihu Robinson. In 1781 he left his native village to become assistant to his cousin George Bewley who kept a school at Kendal. There he passed the next I2 years, be coming in 1785, through the retirement of his cousin, joint man ager of the school with his elder brother Jonathan. He remained at Kendal till, in the spring of 1793, he moved to Manchester, where he spent the rest of his life. Mainly through John Gough (17 5 7-18 2 5 ), a blind philosopher who was a good classical and mathematical scholar, he was appointed teacher of mathematics and natural philosophy at the New College in Moseley Street (in 1889 transferred to Manchester College, Oxford), and that posi tion he retained until the removal of the college to York in 1799, when he became a "public and private teacher of mathematics and chemistry." Encouraged by Gough, Dalton had, while he was at Kendal, contributed solutions of problems and questions on various sub jects to the Gentlemen's and Ladies' Diaries, and in 1787 he be gan to keep a meteorological diary in which during the ing 57 years he entered more than 200,000 observations. He made his own instruments. His first separate publication was Meteor ological Observations and Essays (1793), which contained the germs of several of his later discoveries ; but in spite of the origi nality of its matter, the book met with only a limited sale. In he was elected a member of the Manchester Literary and Philosophical Society, and a few weeks after election he communi cated his first paper on "Extraordinary facts relating to the vision of colours," in which he gave the earliest account of the optical peculiarity known as Daltonism or colour-blindness, and summed up its characteristics as observed in himself and others. This paper was followed by many others on diverse topics. In 1803 he published a paper on the "Absorption of gases by water and other liquids"; containing his "Law of partial pressures." Dalton was a crude experimenter, a good many of his results have since been disproved and none of his investigations com pares with those concerned with the Atomic Theory, with which his name is inseparably associated. It is clear from the notes prepared for his lectures that in his long series of meteorological experiments he was feeling his way towards the Atomic Theory. A study of these papers by Roscoe and Harden (A New View of the Origin of Dalton's Atomic Theory, 1896) shows that the idea of atomic structure arose in his mind as a purely physical con ception, forced upon him by study of the physical properties of the atmosphere and other gases. The first published indications of this idea are to be found at the end of his paper on the "Absorp tion of gases" (Oct. 21, 1803) published in 1805. Here he says: "Why does not water admit its bulk of every kind of gas alike? This question I have duly considered, and though I am not able to satisfy myself completely I am nearly persuaded that the cir cumstance depends on the weight and number of the ultimate particles of the several gases." He proceeds to give what has been quoted as his first table of atomic weights, but on p. 248 of his laboratory notebooks for 1802-04, under the date Sept. 6, 1803, there is an earlier one in which he sets forth the relative weights of the ultimate atoms of a number of substances, derived from analysis of water, ammonia, carbon dioxide, etc., by chemists of the time. Confronted with the "problem of ascertaining the relative diameter of the particles of which, he was convinced, all gases were made up, he had recourse to the results of chemical analysis. He thus arrived at the idea that chemical combination takes place between particles of different weights, and this differ entiated his theory from the historic speculations of the Greeks. The extension of this idea to substances in general necessarily led him to the law of combination in multiple proportions, and the comparison with experiment brilliantly confirmed the truth of his deduction" (A New View, etc., pp. 5o, 51). Dalton communicated his atomic theory to Dr. Thomas Thomson of Glasgow university, who by consent included an outline of it in the third edition of his System of Chemistry (1807), and Dalton gave a further account of it in the first part of the first volume (18o8) of his New System of Chemical Philosophy.
In 1804 Dalton was chosen to give a course of lectures at the Royal Institution, London, where he delivered another course in 1809-10; and in 1822 he became F.R.S. He was a corresponding member of the French Academy of Sciences, and in 1830 he was elected as one of its eight foreign associates in place of Davy. In 1833 Lord Grey's government conferred on him a pension of f150, raised in 1836 to f300. He lived for more than a quarter of a century with his friend the Rev. W. Johns (1771-1845), in George Street, Manchester, where his daily round of laboratory work and tuition was broken only by annual excursions to the Lake district and occasional visits to London, "a surprising place and well worth one's while to see once, but the most disagree able place on earth for one of a contemplative turn to reside in constantly." In 1822 he paid a short visit to Paris, where he met many of the distinguished men of science then living in the French capital, and he attended several of the earlier meetings of the British Association at York, Oxford, Dublin and Bristol. Into society he rarely went, and his only amusement was a game of bowls on Thursday afternoons. He died in Manchester on July 27, See Henry, Life of Dalton, Cavendish Society (1854) ; Angus Smith, Memoir of John Dalton and History of the Atomic Theory (1856), which on pp. 253-263 gives a list of Dalton's publications; and Roscoe and Harden, A New View of the Origin of Dalton's Atomic Theory (1896) ; an essay by Sir William A. Tilden in his Famous Chemists (1920; also ATOM.