228 Reviews — Prof. Bouncy — Ice- Work, Present and Pad. 

 B IE "V" X IE "W S. 



I. Tce-Work. Present and Past. By T. G. Bonnet, D.Sc, 



LL.D., F.R.S., F.S.A., F.G.S., etc. 8vo, pp. 295, with 24 maps 

 and diagrams, and frontispiece from a photograph. (London : 

 Kegan Paul and Co., 1896.) 



THE value of hypotheses or of well-considered inferences from 

 known facts must depend, partly, on the personality of the 

 thinker, on his usual habit of thinking and lines of thought; and 

 partly whether the basis of his inferences rests on direct observation 

 or on statements of facts by others. " Gather facts for yourself and 

 then submit them to inductive reasoning," has been Dr. Bonney's 

 advice to students ; and certainly he has acted on it himself. 



First, he sketches the general and special features of some Alpine 

 regions which offer available evidence of ice-action in various ways, 

 and which he has personally examined (pp. 3-37). Secondly, he 

 reproduces the statements of good observers relative to the Arctic 

 and Antarctic ice-sheets (pp. 38-75). The features and conditions 

 of the Great Aletsch Glacier and its tributaries are described by the 

 author from personal observation. The origin of the ice-river in 

 the fields of dry snow and " frozen snow " of the heights is followed 

 by its slow downward progress, with debris from the mountains, 

 scattered or trailing on its surface. This often falls into the body 

 of the ice by fissures ; but chiefly it forms the moraines along the 

 edges, which ultimately unite at junctions, and altogether become 

 exposed at the melting of the glacier. Both perched blocks and 

 great moraines result. The ice itself is allowed to have some 

 abrading power (p. 10). The debris imbedded in its mass aids it; 

 but more especially the blocks, stones, grit, and sand are ground, 

 and grind the rocks at the bottom of the ice ; and here also, together 

 with mud, they form a "ground-moraine," which is as variable as 

 the dimensions and conditions of the glacier and its imbedded rock- 

 material. Superficial snow and ice melting in sunshine give water, 

 which furrows the surface until lost in crevasses ; and locally waters 

 from the valley-sides plunge beneath the glacier. These all help to 

 augment the ground-moraine, or maintain the chief line of the sub- 

 glacial drainage. Here the pot-holes are made by gurgitation of 

 stones and water, besides the rounded hummocks of the striated, 

 smooth, and more or less polished floor. 



Hence, though local appearances, due to other causes, may be 

 mistaken for some of them, such conditions and phenomena as those 

 mentioned above may be taken to indicate the path of a vanished 

 glacier. This, though nowadays a commonplace statement, is 

 offered by the author in a detailed form from personal observation, 

 as a basis for his inductions. 



Continuing his observations in the valleys below the ends of the 

 glaciers, although the features vary in some degree from place to 

 place, it is evident that far above the bed of the valley the rocks 



