ADDRESS. XXXVll 



the theory in a form in which the use of the term atom would be hypothetical 

 only, and not absolute and indispensable. 



It is always unsafe and perhaps unphilosophical to speculate upon the 

 amount of the good fortune which is connected with the time and circum- 

 stances of any great discovery, with any view to detract from the credit which 

 is due to its author ; but it has been contended that WoUaston, Berzelius and 

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

 generalization, and that it could not long have eluded the vigilant pursuit of 

 those distinguished chemists. In reply to this insinuation, however, we may 

 venture to repeat, what has been often before observed, that if philosophy be 

 a lottery, those only who deserve to win them, ever draw its prizes ; that 

 those only who have scrutinized closely and cautiously the well-known and 

 recognized approaches to the temple of nature, have ever been able to dis- 

 cover the new paths which lead to its unexplored treasures, however plain 

 and obvious, when they are once mnde known to us, they may appear to be. 

 To Dalton this discovery was not due to any momentary philosophical inspi- 

 ration, for which his previous contemplations had not prepared his mind; it 

 was the legitimate result of long and profound reflection upon the relations, 

 which chemical analysis had made known to him, of their separate elements 

 to the gaseous, fluid or solid bodies which they composed, and also of the va- 

 rious circumstances which appeared to determine their combination with each 

 other ; it was, in fact, the capital conclusion, to which his speculations, from 

 the earliest period of his philosophical life, had constantly been tending. 



The atomic theory is not the only great contribution to chemical science 

 which we owe to Dalton ; he discovered contemporaneously with Gay-Lussac, 

 with whom many of his researches 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 pro- 

 ceeding from the temperature of freezing to that of 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 ap- 

 proaches 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 main- 

 tained : the style of his writings, particvdarly in his ' System of Chemical Phi- 

 losophy,' bears strongly the impress of his philosophical character ; it is clear, 

 precise, and unembarrassed ; always equal to his subject, and never above it. 



" Tliough Dalton's great discovery," says the historian of the inductive 

 sciences, " was soon generally employed and universally spoken of with ad- 

 miration, it did not bring to him anything but barren praise, and he conti- 

 nued 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 in 1826, two medals for the encouragement of science having been 

 placed at the disposal of the Royal Society by the King, one of them was 

 assigned to Dalton for his development of the atomic theory. In 1833, at 

 tlie meeting of the British Association ibr the Advancement of Science which 

 was held at Cambridge, it was announced that the King had bestowed upon 

 him a pension of £150* ; at the preceding meeting at Oxford, that University 

 * This was afterwards increased to £300. 



