124 ICE AND GLACIERS. 



two plane wooden boards, instead of in the mould, into which 

 we cannot see. 



I place first an irregular cylindrical piece of natural ice, 

 taken from the frozen surface of the river, with its two plane 

 terminal surfaces between the plates of the press. If I begin to 

 work, the block is broken by pressure ; every crack which forms 

 extends through the entire mass of the block ; this splits into a 

 heap of larger fragments, which again crack and are broken the 

 more the press is worked. If the pressure is relaxed, all these 

 fragments are, indeed, reunited by freezing, but the aspect of the 



FIG. 23. FIG. 24. 



whole indicates that the shape of the block has 'resulted less 

 from pliability than from fracture, and that the individual frag- 

 ments have completely altered their mutual positions. 



The case is quite different when one of the cylinders which 

 we have formed from snow or ice is placed between the plates of 

 the press. As the press is worked the creaking and cracking is 

 heard, but it does not break; it gradually changes its shape, 

 becomes lower and at the same time thicker ; and only when it 

 has been changed into a tolerably flat circular disc does it begin 

 to give way at the edges and form cracks, like crevasses on 

 a small scale. Fig. 23 shows the height and diameter of such a 



