280 Proceedings of the British Association. 



rally known to the world in Dr. Thomson's Chemistry in 1807, and 

 was briefly noticed in his own system of chemistry which appeared 

 in the following year ; and though his claims to this great generaliza- 

 tion were subject to some disputes both at home and abroad, yet in 

 a very short time both the doctrine and its author were acknowledged 

 and recognized by Wollaston, Davy, Berzelius, and all the great che- 

 mists in Europe. But the atomic theory is not the only great con- 

 tribution to chemical science which we owe to Dalton ; he discovered 

 cotemporaneously with Gay-Lussac, with whom many of his re- 

 searches run parallel, the important general law of the expansion of 

 gases — that for equal increments of temperature, all gases expand by 

 the same portion of their bulk, being about three-eighths in proceed- 

 ing from the temperatures of freezing and boiling water. His con- 

 tributions to meteorology were also of the most important kind. Dr. 

 Dalton was not a man of what are commonly called brilliant talents, 

 but of a singularly clear understanding and plain practical good 

 sense ; his approaches to the formation of his theories were slow and 

 deliberate, where every step of his induction was made the object of 

 long- continued and persevering thought ; but his convictions were 

 based upon the true principles of inductive philosophy, and when once 

 formed, were boldly advanced and steadily maintained. It is always 

 unsafe, and perhaps unwise to speculate upon the amount of good 

 fortune which is connected with the time and circumstances of any 

 great discovery, with some view to detract from the credit of its 

 author; and it has been contended that Wollaston, Berzelius and 

 others, were already in the track which would naturally lead to this 

 great generalization ; but it has been frequently and justly remarked, 

 that if philosophy be a lottery, those only who play well are ever 

 observed to draw its prizes. 



" Though Dal ton's great discovery," says the historian of the 

 Inductive Sciences, " was soon generally employed, and universally 

 spoken of with admiration, it did not bring to him anything but bar- 

 ren praise, and he continued in his humble employment when his 

 fame had filled Europe, and his name become a household word in 

 the laboratory. After some years he was appointed a corresponding 

 member of the Institute of France, which may be considered as a 

 European recognition of the importance of what he had done ; and 



