CLOUDS AND RIVERS, ICE AND GLACIERS. 165 



water, and cause them to touch each other ; they freeze 

 together where they touch. You can form a chain of 

 such fragments; and then, by taking hold of one end 

 of the chain, you can draw the whole series after it. 

 Chains of icebergs are sometimes formed in this way 

 in the Arctic seas. 



417. Consider what follows from these observations, 

 Snow consists of small particles of ice. Now if by 

 pressure we squeeze out the air entangled in thawing 

 snow, and bring the little ice-granules into close contact, 

 they may be expected to freeze together ; and if the 

 expulsion of the air be complete, the squeezed snow may 

 be expected to assume the appearance of compact ice. 



418. We arrive at this conclusion by reasoning; let 

 us now test it by experiment, employing a suitable hy- 

 draulic press, and a mould to hold the snow. In exact 

 accordance with our expectation, w r e convert by pressure 

 the snow into ice.* 



419. Place a compact mass of ice in a proper mould, 

 and subject it to pressure. It breaks in pieces : squeeze 

 the pieces forcibly together; they re-unite by regela- 

 tion, and a compact piece of ice, totally different in 

 shape from the first one, is taken from the press. To 

 produce this effect the ice must be in a thawing con- 

 dition. When its temperature is much below the 

 melting point it is crushed by pressure, not into a 



* A similar experiment was made by the Messrs. Schlagintweit prior to 

 t&£ discovery which explains it, and which therefore remained unsolved* 



