HISTORY OF THE ATOMIC THEORY. 49 



ence, physically speaking, equal; and ^he same may be 

 observed of the small lateral force." 



" 8. The greatest difficulty attending the mechanical hypo- 

 thesis arises from different gases observing different laws. 

 Why does water not admit its bulk of every kind of gas alike? 

 This question I have duly considered, and although I am not 

 yet able to satisfy myself completely, I am nearly persuaded 

 that the circumstance depends upon the weight and number of 

 the ultimate particles of the several gases; those whose parti- 

 cles are lightest and single being least absorbable, and the 

 others more, according as they increase in weight and com- 

 plexity — (subsequent inquiry made him think this less 

 probable). An inquiry into the relative weights of the ulti- 

 mate particles of bodies is a subject, as far as I know, 

 entirely new; I have lately been prosecuting this inquiry 

 with remarkable success. The principle cannot be entered 

 upon in this paper; but I shall just subjoin the results, as 

 for as they appear to be ascertained by my experiments." 



He then gives a list of relative weights of 21 substances, 

 constituting the first attempt to form a table of atomic 

 weights. 



" Table of the relative weights of the ultimate particles of 

 gaseous and other bodies. 



Hydrogen 1 



Azot... 4.2 



Carbone 4.3 



Ammonia 5.2 



Oxygen 5.5 



Water 6.5 



Phosphorus 7.2 



Phosphuretted hydrogen 8.2 



Nitrous gas 9.3 



Ether 9.6 



Gaseous oxide of carbone 9.8 



H 



