THE ROLLING-MILL. 



323 



towards each other by mechanical means, such as levers, screws, 

 or springs, or all three combined. These cylinders revolve in 

 opposite directions, and, if any object be placed between them, 

 they draw it through them, and present it on the other side in 

 a flattened condition. 



Many years ago, one of my schoolfellows, who had been 

 brought up entirely under the care of some maiden ladies, 

 was visiting a workshop, and must needs put his finger between 

 two revolving rollers. Of course the hand was drawn between 

 them, and simply squeezed flat. The machine was instantly 

 stopped, and the hand extricated ; and the strange thing was, 

 that the crushed and shapeless hand afterwards recovered its full 



JAWS OF SKATE. 



CRUSHIXG-MILL AND ROLLER. 



power, though not its shape, and was able to touch the keys of 

 the piano. 



The whole process of the Boiling-mill is singularly inter- 

 esting, whether it be used for large or small objects. 



Supposing that the grooved rollers of the illustration were 

 cut across so as to present a number of points, it is evident 

 that anything which got between them would be bitten to 

 pieces, each piece being of a tolerably uniform shape. 



This plan is now adopted in the granulation of gunpowder. 

 After the future powder has emerged from the hydraulic 

 press in the form called " press-cake," it was formerly broken 

 to bits with wooden or copper mallets, and then placed in a 

 very peculiar kind of sieve. This was shaped like an ordinary 

 sieve, but the bottom was made of cowhide, pierced with 

 innumerable holes. A round pebble was placed in the sieve, 

 and, when the latter was violently shaken backwards and for- 



y 2 



