Dalton, during his residence at Kendal, had occasionally contributed to 'The Gentleman's and Lady's Diary,' and in 1768 had commoneed a series of meteorological records and observations, the first Jesuits of which he published soon after he weut to Manchester, under thd title of ' Meteorological Observations and Eeartys,'Svo, 1703. Ile continued the habit of observing cud recording the state of the atmosphere with the greatest regularity till the day before he died, taking several records daily; he had registered altogether upwards of 200,000 independent notices. his first essay in the ''Transactions of the Manchester Literary and Philosophical Society,' related to a peculiarity of his own sight—that of inability to distinguish certain colours—and was entitled ' Extraordinary Facts relating to the Vision of Colours, with Observations, by Mr. John Dalton.' It was read October 31, 1794, and is inserted in the' Tmeteactions; vol. v., part I. This peculiarity of vision has been since very generally designated Daltoniun. lu 1e01 he published ' Elements of English Grammar,' London, 8vo.
In the 'Manchester Transactions' for 1802, part ii., there are six papers by Dalton, chiefly on subjects of meteorology, of which the moat important is one called 'Experimental Essays on the Constitution of Mixed Gases; on the Force of Steam, or Vapour from Water and other Liquids, in different Temperatures, both in a Torricellian Vacuum and in Air; on Evaporation ; and on the Expansion of 0344:8 by Heat.' lie discusses with great acuteness the difficult problem of the elml diffusion throughout each other of gases of uuequal densities; aud, besides other facts of importance, he proves that water, when it evaporates, is always converted into an elastic fluid or vapour, and that the elasticity of this vapour increases as the temperature increases; at 32° of Fahrenheit it balances a column of mercury about half an inch in height ; at 212° it balance% A column thirty inches high, or is equal to the pressure of the atmosphere. lie deter mines the elasticity of vapour et all temperatures from 32° to 212°, points out the method of determining the quantity of vapour which exists at any time In the atmosphere, and determines the rate of evaporation from the surface of water at all temperatures from 32° to 212'. The principles laid down in these essays have been of the highest importance to chemists in their investigations respecting the specific gravity of gases, and havo enabled them to solve many interesting problems.
Dalton began to work out his grand discovery of the atomic theory In 1803; in August 1801 he explained it distinctly and fully to Dr.
Thomas Thomson, who was then on a short visit to Manchester ; he touched upon it in a lecture before the Royal Institution of London in 1804, and subsequently in lectures at Manchester, Edinburgh, and Glasgow ; but Dr. Thomson was the first to publish it short eketch of it. iu 1807, in the third edition of his 'System of Chemistry.' III 18113 Dalton published 'A New System of Chemical Philosophy,' 8vo, vol. L In the first chapter he trenta of heat; in the second, of the constitution of bodies, In which his chief object is to oppose tho peculiar notions respecting elastic fluids which had been advanced by Berthollet and were supported by Dr. Murray of Edinburgh; in the third chapter, which occupies only a few pages, he gives the outline of the atomic theory. In a plate at the end of the volturio he gives the symbois and atomic weights of 37 bodies, 20 of which were then considered simple, and the 17 others compelled. In the second volume of his ' New System of Chemical Philosophy,' published in 1810, he treats of the elementary principles, or simple bodies, oxygen, hydrogen, azote, carbon, sulphur, phosphorus, and the metals ; next he treats of the oxygen combined with hydrogen, azote, carbon, sul phur, and phosphorus; and of hydrogen combiued with ante, carbon, sulphur, and phosphorus ; finally, he treats of the fixed alkalies and earths. The table of atomic weights at the end of this volume, though more complete than the one he had given at the end of the first volume, is still very imperfect.
The atomic theory is undoubtedly one of the most important contri butions which has ever been made to chemistry ; and hardly leas important were Dalton's attempts to determine the atomic weights of the different substances, though scarcely a single number was deter mined correctly. At the time when he made his discovery there was not a single chemical analysis which could properly be considered as correct; there was not a single gas whose specific gravity was known with any approach to accuracy ; and Dalton displayed infinite sagacity at coming so near the truth as he did. Since the introduction of the atomic theory, the knowledge of chemical combination has beau sim plified to an amazing extent, and the processes of analysis, which constitute the essence of chemistry, have assumed a degree of accuracy almost approaching to mathematical precisiou. Manufactures have been benefited as well as science ; the quantity of each constituent of any article can be regulated with perfect accuracy, so that there is no waste, and tho result of the combination can be reckoned upon with unfailing certainty.