HISTORY OF THE ATOMIC THEORY. 237 



** An atom of water or steam composed of one oxygen and 

 one hydrogen, &c. = 8," and so on with other bodies. 



This is the result of enormous labour, added to that of the 

 many gaseous analyses. Let no one say that because the atomic 

 weights are in most cases inexact he shews want of power. 

 We have seen in our own days how difficult it is to get an 

 exact atomic weight, we have found that it needs the com- 

 bined forces of several laboratories to settle one to satisfaction, 

 and we must rather admire that man who approached first so 

 near. But, although Dalton has been called a rough worker, 

 and I am not prepared to deny it, we must remember that his 

 analyses are not behind the time, but in advance of it in early 

 life. At the period when he was working out this theory, the 

 analyses of all chemists were in general only approximative. 

 Fine analysis was only then beginning its course. But as 

 Dalton says, "it is not necessary to insist on the accuracy 

 of all these compounds, both in number and weight; the 

 principle will be entered into more particularly hereafter, as 

 far as respects the individual results."* 



He also says, "it is not to be understood that all those 

 articles marked as simple substances, are necessarily such by 

 the theory ;" ex, gr,y soda and potash are mentioned as com- 

 pound. 



In various parts of his work we learn exactly the method 

 in which he applied his theory, and as he devoted his time 

 to its illustration, we are not left in any doubts as to his 

 opinions. 



We have now to find exactly what new ideas he produced. 

 We have seen in the last chapter the state of chemical 

 opinion, the prevalence of the Berthollet philosophy, and the 

 uncertainty hanging over the opinions opposed to his. 

 General opinion on combination was in reality not more 

 advanced than in the earliest days of the science. Dalton 

 found matters in this state of confusion, and we have seen the 



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