438 REVIEWS 



not show signs of extensive retreat. In 191 2, however, the glacial fronts 

 seemed to be generally receding. Three glaciers of Blaesdal, Disco 

 Island, were found to have retreated during the past fifteen years, con- 

 tinuing a preceding recession. 



Marine terraces gave other evidence of local glaciation. In the 

 vicinity of Kuk (lat. 66°48'N., long. 52° 17' W.) and Sarfanguak, the 

 lowest terrace was at 40 m. above sea-level, and was composed of a layer 

 of till, covered with marine-laid sediments, another layer of till, and a 

 top layer of mussel-bearing sand. Evidently, during the formation of 

 these deposits, the land was depressed and the tongue of the valley glacier 

 supplying the sediments retreated, advanced, and retreated again. The 

 character of the fossils indicates a climate at that time too warm to have 

 been associated with inland ice as far out as this. 



The expedition was able to make some valuable observations of ice- 

 bergs. Icebergs, even though tabular at the start, usually were so 

 melted and exploded that they did not reach the open sea as large masses. 

 Many bergs carry portions of sub-glacial caverns, which are visible in 

 various stages of destruction. Calving takes place by hydrostatic lift- 

 ing, or by falUng or pushing off. As this occurs there is much exploding 

 from the sudden release of the highly compressed air in the glacier. This 

 air goes into the glacier with the original snow, and the increasing weight 

 piled on top of it brings on enormous compression which, when suddenly 

 released by calving, hurls a berg into a thousand pieces in successive 

 explosions. In Disco Bay the sizes of icebergs ranged up to 75 m. high 

 and 640 m. long.^ 



Charles F. Brooks 



Earth Evolution and its Facial Expression. By William H. Hobbs: 

 Pp. xvii-l-178, plates 6, figs. 84. New York: The Macmillan 

 Co., 1921. 



This volume of 178 pages is well printed on good paper, and is illus- 

 trated with many diagrams and sketches. Although it seems to be 

 addressed to the general reader, it is rather too technical for any but 

 trained students of the earth sciences. 



In the opening chapters, the author outlines the progress of ideas 

 regarding the state and origin of the earth, and concludes that Laplace's 

 theory is now generally discredited, while that of Chamberlin ''has the 

 most general support among students of earth science." He also decides 



' A discussion of the maintenance and ablation of tlie inland ice is included in a 

 review published in the Geographical Review, July, 1923. 



