EXTENSIVE USE OF HEAT. 



powers or principles, for the three that have been 

 stated, are perfectly sufficient to produce every 

 appearance and every change of appearance that 

 we can imagine for we can rationally imagine 

 nothing but a modification of something we, by 

 the operation of mind, have seen altered in its re- 

 lation ; and it is no more violation of propriety to 

 suppose that the same heat which keeps the body 

 warm in life, which labours in the furnace and 

 cooks in the fire, and which brings us the beauty 

 of summer and the abundance of autumn, can 

 sport in the aurora-borealis, guide mariners in the 

 needle, or blaze in the lightning, than it is to 

 suppose that the never-thawing ice of Mont- 

 Blanc could be a river or part of a tree, or a 

 human body, or that its component parts might 

 become the fuel of the most intense flame that is 

 known, and that they are the chief materials in 

 the flames of our common fires. 



At whatever place of the atmosphere water 

 remains in a state of rest, the heat is always such 

 as to balance to the utmost nicety both the gravi- 

 tation and the cohesion ; and it is only the air which 

 at the same point admits of variation. The others 

 are compared with it dull and passive properties ; 

 and they act only when heat is suspended, though 

 when once begun, they increase at the rate which 

 has been mentioned ; and, as their action goes on, 

 and water has no solid cohesion at a temperate 

 heat, the result is most conspicuous as gravi- 

 tation. 



The extreme mobility of the air favours the ac- 

 tion of all these principles : and that is the reason 

 why the aerial state is to be regarded as the ele- 

 mentary state in the formation of all material 

 things. Easily as the air is moveable at the sur- 



