The Theory of Glacier motion. 8 1 



glacier crystals increases progressively from the higher part 

 of the glacier to the lower, and that they are in a state of 

 gradual growth. This observation has been amply confirmed 

 (/</.9.,etc.),and notably byBertin andGrad, who employed the 

 polariscope for the purpose. It must be confessed that the 

 process here described presents some very great puzzles 

 and difficulties for the physicist. How the crystals in a 

 compact mass of ice can grow from the size of small nuts 

 to that of a hen's ^%%^ granting even that the growth takes 

 centuries to develope, is a very great puzzle. They clearly 

 can only grow by in some way attracting fresh water to 

 themselves. Hugi supposed that the water which they 

 enlist comes to them in the form of atmospheric vapour, 

 since his experiments had shewn him that the mass of the 

 glacier was not permeable to liquids, a result in which, as 

 we have seen, he was confirmed by Huxley, and he further 

 went on to urge that it was by this growth that the 

 movement of ice in glaciers is in fact produced. 



Grad contended that in his own experiments infiltration 

 of water was shewn to be possible {Comptes-Rendus, CXIX. 

 957), and went on to urge that the cause of glacier move- 

 ment is the infiltration of water into the capillary fissures 

 and its subsequent freezing on the crystals of ice forming 

 the glacier, which are consequently enlarged and made to 

 assume a constant instead of a heterogeneous direction like 

 those of frozen water. The expansion thus caused developes 

 a general movement of the ice in the direction of least 

 resistance, in other words, he says, " la masse meme du 

 glacier s'accroit par intersusception, et c'est ce developpe- 

 ment ou cette croissance qui provoque le mouvement" 

 {Comptes-Rendus for 1867, Vol. LXIV. 46 — 47). 



Practically the same views were pressed at greater length 

 and with greater elaborateness by Forel, who, in 1882, 

 published a paper in the Archives des Sciences physiques et 

 naturelles of Geneva entitled, " Le Grain du Glacier." He 



