CHAP, ix.] VARIOUS APPLICATIONS OF STEAM. 



489 



very large size. The work may be done by its help, in one heating 

 which effects a saving of time, fuel, and metal. 



The effect of this powerful engine is equal to that produced by a 

 weight of sixteen tons, striking forty strokes a minute. The alternate 

 double and single action can be obtained instantaneously. By means 

 of a slide-valve suitably placed, the fall and the force of the blow can 

 be equally changed in an instant. We know that for hammers which 

 act by their gravity, the mechanical work produced is represented by 

 the weight of the mass multiplied by the height of the fall. The 



FIG. 328. Steam block-rammer : section of the cylinder. 



weight of the whole apparatus including the mass of the hammer, the 

 anvil, the block, and the steam-engine, &c., is about 100 tons. The 

 head of the Woolwich hammer weighs thirty tons, and when forced 

 down by the whole power of the steam, it comes down upon the hot 

 iron with an energy of more than 1000 foot-tons, the solid ground 

 trembling for a great distance around in spite of piles, stone and 

 concrete foundations more than fifty feet deep. 



In great workshops, manufactories of engines, forges, and saw- 



