MOTIVE POWER OF HEAT. 39 



fected that it can be set up and supplied with fuel 

 at small cost, it will combine all desirable qualities, 

 and will afford to the industrial arts a range the 

 extent of which can scarcely be predicted. It is 

 not merely that a powerful and convenient motor 

 that can be procured and carried anywhere is 

 substituted for the motors already in use, but that 

 it causes rapid extension in the arts in which it is 

 applied, and can even create entirely new arts. 



The most signal service that the steam-engine 

 has rendered to England is undoubtedly the 

 revival of the working of the coal-mines, which had 

 declined, and threatened to cease entirely, in con- 

 sequence of the continually increasing difficulty of 

 drainage, and of raising the coal.* We should 

 rank second the benefit to iron manufacture, both 

 by the abundant supply of coal substituted for 

 wood just when the latter had begun to grow scarce, 



*It may be said that coal-mining has increased tenfold 

 in England since the invention of the steam-engine. It is 

 almost equally true in regard to the mining of copper, tin, 

 and iron. The results produced in a half-century by the 

 steam-engine in the mines of England are to-day parallel- 

 ed in the gold and silver mines of the New World mines 

 of which the working declined from day to day, prin- 

 cipally on account of the insufficiency of the motors em- 

 ployed in the draining and the extraction of the minerals. 



