166 THE FORMS OF WATER IN 



pellucid mass of another shape, but into a white 

 powder. 



420. By means of suitable moulds you may in this 

 way change the shape of ice to any extent, turning out 

 spheres, and cups, and rings, and twisted ropes of the 

 substance; the change of form in these cases being 

 effected through rude fracture and regelation. 



421. By applying the pressure carefully, rude fracture 

 may be avoided, and the ice compelled slowly to change 

 its form as if it were a plastic body. 



422. Now our first experiment illustrates the con- 

 solidation of the snows of the higher Alpine regions. 

 The deeper layers of the neve have to bear the weight 

 of all above them, and are thereby converted into more 

 or less perfect ice. And our last experiment illustrates 

 the changes of form observed upon the glacier, where, 

 by the slow and constant application of pressure, the ice 

 gradually moulds itself to the valley, which it fills. 



423. In glaciers, however, we have also ample illus- 

 trations of rude fracture and regelation. The opening 

 and closing of crevasses illustrate this. The glacier 

 is broken on the cascades and mended at their bases. 

 When two branch glaciers lay their sides together, the 

 regelation is so firm that they begin immediately to 

 flow in the trunk glacier as a single stream. The 

 medial moraine gives no indication by its slowness of 

 motion that it is derived from the sluggish ice of tlis 

 sides of th^ branch glaciers. 



