1846.] IMPORTANCE OF CREVASSES USUALLY OVERRATED. 143 



Crevasses In the second place, I maintain that actual in- 

 spection shows that a glacier is not the mass of fragments nor 

 of parallelopipedons which some persons have, naturally enough 

 at first sight, supposed it to be. In truth there is not an 

 approach to such a condition in those glaciers which move over 

 moderate slopes of considerable extent, which have very properly 

 been assumed by all writers as the criterial examples of any 

 theory; for it is not denied that portions of glaciers and glacier 

 tributaries do sometimes fall piecemeal over precipices, each 

 fragment descending by its separate and individual gravity, in 

 the manner of an avalanche, although I am disposed to believe, 

 indeed am sure, that the number of such instances is smaller 

 than is usually imagined ; and the angle requisite for such a 

 tumultuous mode of descent is far greater than it has, perhaps, 

 always hitherto been considered to be. To him who would 

 form a just estimate of the mechanical constitution of a glacier 

 who would consider it as a whole without always distracting 

 his attention from the length and breadth of the problem by a 

 minute attention to its lesser features, I would earnestly 

 recommend the frequent and attentive survey of a glacier or 

 glaciers from a considerable elevation above their level and 

 under varying effects of light. Had I confined myself to 

 studying crevasses on the surface of the glacier, measuring 

 their depths, injecting the ice with fluids and taking its tem- 

 perature ; useful and important as these inquiries are (and I 

 might almost include the fundamental and most important 

 inquiry of all, that of ascertaining the velocity of its parts), I 

 should have been much longer in seizing the general truth of 

 the individual character of a glacier, the importance of the 

 fluid-like connection of its parts, the perfectly secondary 

 importance or unimportance of the fissures by which it is often 

 traversed. The traveller who winds his tortuous and sometimes 

 perilous path among these crevasses, forgets, in the fatigue of 

 his circumventions, in the wonder of his curiosity at their 

 beauty and seemingly unfathomable depth, in the appalling 

 steepness of their sides and the comparative insecurity of his 



