170 HISTORY OF CHEMISTRY. 



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 of England, one of them was 

 assigned to Dalton, "for his developement of the 

 atomic theory." In 1833, at the meeting of the 

 British Association for the Advancement of Science, 

 which was held in Cambridge, it was announced that 

 the king had bestowed upon him a pension of 150; 

 at the preceding meeting at Oxford, that university 

 had conferred upon him the degree of Doctor of 

 Laws, a step the more remarkable, since he be- 

 longed to the sect of Quakers. At all the meetings 

 of the British Association he has been present, and 

 has always been surrounded by the reverence and 

 admiration of all who feel any sympathy with the 

 progress of science. May he long remain among 

 us thus to remind us of the vast advance which 

 Chemistry owes to him ! (H). 



Sect. 3. The Theory of Volumes. Gay-Lussac. 



THE atomic theory, at the very epoch of its intro- 

 duction into France, received a modification in 

 virtue of a curious discovery then made. Soon 

 after the publication of Dalton's system, Gay-Lussac 

 and Humboldt found a rule for the combination of 

 substances, which includes that of Dalton as far as 

 it goes, but extends to combinations of gases only. 

 This law is the theory of volumes; namely, that 

 gases unite together by volume in very simple and 



