QQ Sa'mtific Intelligence. 



The present state of the question. — The condition which the per- 

 plexing question of the cause of the descent of uliuiers has noi 

 reached seems to be something like the following. The ice of a 

 glacier is not in a soft and plastic state, but is solid, hard, hrittle, 

 and unyielding. It nevertheless behaves in some respects in a 

 manner very like what a soft and plastic substance would do if 

 placed in similar circumstances, inasmuch as it accommodates 

 Itself to all the inequalities of the channel in which it moves, 

 The ice of the glacier, though hard and solid, moves with a dif- 

 ferential motion ; the particles of the ice are displaced over each 

 other, or, in other words, the ice shears as it descends. It had 

 been concluded that the mere weight of tlu- uiacier was sufficient 

 to shear the ice. Canon Moseley has iiiv(^>tiizaie(l tliis point, and 



way that it is supposed to do, it wouhl require a force some thirty or 

 forty times as great as the weight ol the glacier. Consequently, for 

 the glacier to descend, a force in addition to that of gravitatiou is 

 required. What, then, is this force ? It is found that the rate at 

 which the glacier descends depends uY><.m the ainoiiut of heat irliiofi 

 it is receivmg. This shows that the motion of the glacier is in 

 some way or other dependent upon heat. Is heat, then, the force 

 ' f? Theans "" ' " " ' ' 



.rily require( , 



other till we see whether or not heat will sutiice. In what way, 

 then, does heat aid gravitation in the descent of the glacier? In 

 what way does heat assist gravitation in ti ' ' " ' " '""' 

 There are two ways whereby we may coi 



ice forward, or it may assist gravitation liy 

 sion of the particles, and tJiiis allowintr ! 

 motion which it otherwis»' coiiM not |,i<,. 

 which has yet been made to explain \m<\\ \n 

 pushing the ice forward, has failed. 'I lie 

 expand the ice of the glacier niav Ik- n-an 

 that it does not act as a force impelling; tiir 

 we are thus obliged to turn our attfutinti t 

 viz., that heat assists gravitation to shear 

 pressure, but by diminishing tlie cohesive t 

 ' > enable gravitation to ]>ush the one pas 



,-?l.il!<MheMhe- 



is this done? Does heat diminish the cohesion by acting as an 

 because it cannot expand the ice ofThe glacier ; and besides, y«fe 

 It to do this, it would destroy the solid and firm character ot w 

 ice, and the ice of the glacier would not then, as a mass, poss*^ 

 the great amount of shearing-force which observation and expe" 

 ment show that it does. In short it is because the particles oi ^^^ 

 ice are so firmly fixed together at the time that the glacier i8 _ 

 scendmg, that we are obliged to call in the aid of some othertort^ 

 m addition to the weight of the glacier to shear tlie ice. i^^' 

 does not cause displacement of the particles by making the i 

 soft and plastic ; for we know that the ice of the glacier is°o*»o^j, 

 and plastic, but hard and brittle. The shearing-force of the ice 



