REVIEWS. 43 



to support. At this season, their long winter coat of hair came off by handfulls. 

 They make a low grunting noise almost like a pig ; the milk is very small in quan- 

 tity and excessively rich." 



The theory of glacier motion, communicated by Professor Forbes in his 

 former work, is that — " A glacier is an imperfect fluid, or a viscous body, 

 which is urged down slopes of a certain inclination by the mutual pressure 

 of its parts. When we think of a mass of Wenham ice on our dinner 

 tables, flying into fragments on slight acupuncturation, we are not prepared 

 to consider it as a plastic body, yet such it surely is, when we view it in 

 the enormous masses of the glacier — squeezing through defiles of varying 

 breadth, spreading out where there is space, and passing, by extension, 

 longitudinally when the gorge narrows; yet though this plastic nature, 

 subject to the enormous pressure it occasionally bears, will account 

 for the slow descent of the glacier, and though we fully agree with 

 the general philosophic views of the author, we do think he has ne- 

 glected to give to hydrostatic pressure its full value in facilitating the 

 motion in question. 



In 1838, our learned countryman, Robert Mallet, gave to the Geological 

 Society of Dublin, a most excellent paper on the mechanism of glaciers. 

 He there very clearly showed how the glaciers may be water borne for a 

 while, until the escape of the water below resulted in a downward motion 

 of the mass above. Every schoolboy knows the hydrostatic paradox, that 

 a drop of water will float a man of war, so will a drop float a glacier. 

 When we see workmen with levers urging along some enormous mass of 

 stone, it is scarcely moveable until a roller is placed beneath, so with the 

 glacier, the mighty forces to which it is subjected, and its plastic nature 

 may admit of some motion ; yet we believe it would be small, but for 

 the lifting power below. Never having seen a glacier, we feel diffident in 

 thus expressing an opinion which would, probably, have been unnecessary 

 had Professor Forbes noticed Mr. Mallet's papers on the subject, as he has 

 those of Esmarh and others. The observations of Professor Forbes, in 

 Norway, go to confirm his views as formed in Switzerland, that the glacier 

 moves as £ great river, allowance being made for its immensely greater vis- 

 cosity. Be it so; but it has helps which the river has not, we think. 

 Amongst others, freezing of water in the crewasses, if it be so, would be a 

 mighty power, pushing forward where there was least resistance. 



We consider that it may, perchance, be useful to give such circulation to 

 the desiderata of our author as our pages can supply ; we, therefore, 

 here insert them. 



" I will briefly refer to a few of the many observations desirable to be 



