254 ON GLACIERS IN GENERAL. 



The viscous theory of glaciers, as deduced from observa- 

 tion by the present writer, though now very generally accepted, 

 had to struggle with numerous and strongly-urged objections ; 

 of which the oftenest repeated was, that ice is by its nature a 

 brittle solid, and not sensibly possessed of any viscous or plastic 

 quality. In answer to this, it may be urged that the qualities 

 of solid bodies of vast size, and acted on by stupendous and 

 long-continued forces, cannot be estimated from experiments on 

 a small scale, especially if short and violent ; that sealing-wax, 

 pitch, and other similar bodies mould themselves, with time, to 

 the surfaces on which they lie, even at atmospheric tempera- 

 tures, and whilst they maintain, at the same time, the quality 

 of excessive brittleness under a blow or a rapid change of form ; 

 that even ice does not pass at once, and per saltum, from the 

 solid to the liquid state, but absorbs its latent heat throughout 

 a certain small range of temperature (between 28'4 and 32 of 

 Fahrenheit) , which is precisely that to which the ice of glaciers 

 is actually exposed ; that, after all, a glacier is not a crystalline 

 solid, like ice, tranquilly frozen in a mould, but possesses a 

 peculiar fissured and laminated structure, through which water 

 enters (at least for a great part of the year) into its intrinsic 

 composition. But, waiving the inferences from all these facts, 

 the main argument in favour of the view now maintained is 

 this, that admitting the preceding propositions as to the velocity 

 of its parts (which no one now contests), the quasi-fluid or 

 viscous motion of the ice of glaciers is not a theory but a FACT. 

 A substance which is seen to pour itself out of a large basin 

 through a narrow outlet without losing its continuity, the 

 different parts of which, from top to bottom, and from side to 

 centre, possess distinct, though related velocities which moves 

 over slopes inconsistent with the friction between its surface 

 and the ground on which it rests which surmounts obstacles, 

 and, even if cleft into two streams by a projecting rock, instead 

 of being thereby anchored as a solid would necessarily be, 

 reunites its streams below, and retains no trace of the fissure, 

 leaving the rock an islet in the icy flood a substance which 



