18 BLACK. 



We have now gone through the whole of this in- 

 teresting subject, rather occupied in contemplating the 

 foundations of a new science than in tracing the exten- 

 sion of the boundaries which confine an old one. The 

 universal operation of heat, and the agency which, by 

 its absorption and its evolution, it exerts on the struc- 

 ture of all bodies, renders the discovery of its nature 

 and action in these respects, next to that of gravitation, 

 the most important step which has been made in the 

 progress of physical science. The new field opened to 

 philosophical inquiry by the discovery of the gaseous 

 bodies is only second to the former step in the import- 

 ance of its consequences. It is as objects of pure 

 science, the mere contemplation of scientific truth, 

 that we have been considering these great discoveries ; 

 yet they have amply contributed also to the advance- 

 ment of the arts. The illustrious improver of the steam 

 engine was too young to have joined in the experiments 

 on fixed air ; but in the course of those by which latent 

 heat was discovered, he had a constant and confidential 

 intercourse with Black, one of his earliest patrons ; 

 and although it is as certain that he did not owe to 

 that philosopher's suggestions any of the steps by which 

 his inventions were compassed, as it is that he had him- 

 self no share in Black's great discovery, it cannot be 

 doubted that the knowledge thus acquired of the true 

 nature of heat, of steam, of evaporation, and of con- 

 densation, contributed most essentially to his mighty 

 improvements. As for the gases, it would be difficult 

 to name the branch of art which has not in some 

 manner and to some extent gained by their discovery. 

 So that the great man whose history we are contem- 

 plating, had the satisfaction of seeing the triumphs of 

 his youth bear fruit in every direction, exalting the 

 power and increasing the comforts of mankind as well 

 as extending the bounds of their knowledge and en- 

 larging the range of their industry. He was but 

 twenty -four years old when he made his first discovery. 



