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WA TT. 



THE intimacy of Mr. Watt with Dr. Black from his 

 earliest years has been already mentioned. When the 

 latter was a Professor at the University of Glasgow, 

 Watt, then a young man, was employed as mathe- 

 matical instrument maker to the Natural Philosophy 

 class, and was in daily communication with the Pro- 

 fessor while his experiments on heat, evaporation, and 

 condensation were carried on. I well remember him 

 afterwards, in his lectures at Edinburgh, mentioning 

 that his young coadjutor employed himself at the same 

 time in researches upon the nature of steam ; and it is 

 certain that his subsequent inventions were greatly 

 aided by the discoveries of Black respecting heat. To 

 the inquiries out of which these inventions arose, he 

 appears to have been led by the accident of having a 

 model of an engine to repair for the Professor of 

 Natural Philosophy. But, before examining the 

 foundations upon which his great and well-earned fame 

 rests, it is fit that we should first consider the state in 

 which he found the engine, which he almost created 

 anew. This is following the same course which has 

 been pursued with respect to the discoveries of Dr. 

 Black. 



The power of steam is far too generally perceived in 

 the ordinary affairs of life to have wholly escaped the 

 observations of men at any period. The ancients ac- 

 cordingly were so far acquainted with it as to have 

 constructed an instrument, the Eeolipile, composed of a 

 metallic ball, which having some water in its bottom, 

 was placed in the fire, and the steam issuing through a 



