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LECTUKE VI. 



THE CORRELATION OF THE PHYSICAL FORCES. 



WE have frequently seen, during the course of 

 these lectures, that one of those powers or forces 

 of matter, of which I have written the names on 

 that board, has produced results which are due 

 to the action of some other force. Thus, you 

 have seen the force of electricity acting in other 

 ways than in attracting; you have also seen it 

 combine matters together or disunite them by 

 means of its action on the chemical force ; and 

 in this case, therefore, you have an instance in 

 which these two powers are related. But we 

 have other and deeper relations than these ; we 

 have not merely to see how it is that one power 

 affects another how the force of heat affects 

 chemical affinity, and so forth, but we must try 

 and comprehend what relation they bear to 

 each other, and how these powers may be 



