REVIEWS 517 



If next we look over all the outstanding features of Antarctic glacia- 

 tion, as set forth in this report, in an endeavor to catch the one which, 

 aside from superior dimensions, most distinguishes it from the glaciations 

 of the Arctic regions and the high altitudes of mid-latitudes, we think it 

 will be found in the great display of the initial and growing stages of glacia- 

 tion, as distinguished from the mature and vanishing stages. There are 

 unparalleled snow-fields and neve-fields ; and great displays of the lower 

 orders of solidification of the glacier type; but the higher orders of com- 

 pact glacier ice are remarkably scant. A part of the explnaation is well 

 recognized, though perhaps not emphasized as much as it might well be. 

 The collecting grounds are large, the mean slope is gentle, the average 

 temperature low, melting almost absent, consolidation by granular 

 growth slow in the absence of much water, and the mean motion meager, 

 so that, before the great mantle has reached a highly compacted stage and 

 entered upon much forceful shearing work, the sea level is reached and the 

 partially solidified mantle is floated away in the form of great tabular 

 icebergs. These are so porous in appearance that they are sometimes 

 called "snowbergs." This term overstrains the facts of the case, but it 

 helps correct the intimation that Antarctica displays the full cycle of a 

 typical glacier. We shall have occasion to return to this in reviewing the 

 subjects of glacial structure and glacial motion. Antarctica tells with 

 wonderful impressiveness the story of a glacier's birth and early growth, 

 but the story is cut off in early youth before the stiffer work of the glacier's 

 maturity has begun. Some of the overenthusiastic expressions of the 

 authors about the superior instructiveness of Antarctic glaciation need 

 to be quahfied by emphasizing Antarctica as a field of surpassing oppor- 

 tunity for the study of snow and snow-fields, of neve and neve-fields, of 

 icebergs, and of sea-ice, but by emphasizing also that it falls far below the 

 Arctic lands and some mid-latitude tracts in facilities for the study of the 

 more solid phases of glacier ice and that forceful shearing action which 

 grinds rock -flour, scores imbedded material and the glacier's bed, and thus 

 leaves the distinctive marks by which ancient glaciations are chiefly 

 identified. 



In view of the unparalleled resources of the Antarctic field for the 

 study of snow and neve, it was both natural and appropriate that the early 

 chapters of the report should center on the formation of snow crystals, 

 their growth into the granules of the neve, and the transition thence into 

 glacier ice. It is natural also for the reader to expect, in view of the 

 opportunity, a discussion of the growth of granules of snow into neve and 

 of neve into glacier ice of like high order. In most respects this expecta- 



