158 THE HISTORY OF SCIENCE 



John Dalton (1766-1844) was born in Cumber- 

 land, went to Kendal to teach school at the age of 

 fifteen, and remained in the Lake District of England 

 till 1793. In this region, where the annual rainfall 

 exceeds forty inches, and in some localities is almost 

 tropical, the young student's attention was early 

 drawn to meteorology. His apparatus consisted of 

 rude home-made rain-gauges, thermometers, and ba- 

 rometers. His interest in the heat, moisture, and 

 constituents of the atmosphere continued throughout 

 life, and Dalton made in all some 200,000 meteoro- 

 logical observations. We gain a clue to his motive 

 in these studies from a letter written in his twenty- 

 second year, in which he speaks of the advantages 

 that might accrue to the husbandman, the mariner, 

 and to mankind in general if we were able to predict 

 the state of the weather with tolerable precision. 



In 1793 Dalton took np his permanent residence 

 in Manchester, and in that year appeared his first 

 book, Meteorological Observations and Essays. 

 Here he deals, among other things, with rainfall, the 

 formation of clouds, evaporation, and the distribution 

 and character of atmospheric moisture. It seemed 

 to him that aqueous vapor always exists as a distinct 

 fluid maintaining its identity among the other fluids 

 of the atmosphere. He thought of atmospheric mois- 

 ture as consisting of minute drops of water, or glob- 

 ules among the globules of oxygen and nitrogen. He 

 was a disciple of Newton's (to whom, indeed, Dalton 

 had some personal likeness), who looked upon matter 

 as consisting of " solid, massy, hard, impenetrable, 

 movable particles, of such sizes and figures, and with 

 such other properties, and in such proportion, as 



