November i6, 191 i] 



NATURE 



7^ 



GLACIERS AND ICE-SHEETS. 

 Characteristics of Existing Glaciers. By Prof. W. H. 

 Hobbs. Pp. XXV + 301. (New York: The Mac- 

 millan Co.; London: Macmillan and Co., Ltd., 

 1911.) Price 135. 6d. net. 



THE framework of this volume was laid by Prof. 

 Hobbs in three papers, dealing in turn with 

 "Mountain Glaciation," "The Ice of Arctic Regions," 

 and "Antarctic Ice," which were published during 

 1910 in scientific journals respectively in London, 

 Philadelphia, and Berlin. The author has done good 

 service to the glaciologist and glacial geologist in 

 bringing together his concise description and classifica- 

 tion of existing glaciers and ice-sheets in the present 

 convenient form. Especially in the parts devoted to 

 Arctic and Antarctic ice he has made an exhaustive 

 digest of the scattered literature, and has presented a 

 copiously illustrated summary of the available in- 

 formation respecting the distribution and character of 

 the ice of these regions. To the end of each chapter 

 he appends a full list of his authorities, so that the 

 book is in every respect a most useful work of refer- 

 ence. His outlook is throughout that of a physio- 

 grapher of the modern American school, and he has 

 constantly in view the effect of ice and snow upon the 

 shape of the land beneath it. 



In his treatment of mountain glaciers, in the first 

 (and shortest) part of his book, the author asserts 

 himself more prominently than in the later parts, and 

 it may be that some of his readers will consider the 

 ralue of this part as a digest has, in consequence, 

 been impaired. He reduces the existing Alpine 

 g;laciers to their really insignificant position by the aid 

 jf comparative diagrams {e.g. plate ii.). He will not 

 lUow that any of them, with the possible exception 

 jf the Great Aletsch, are worthy even of being called 

 /alley-glaciers — " In reality the glaciers of the Alps, 

 "ar from occupying valleys, do not even fill the mother 

 :irques at the valley heads " (p. 52). His rather 

 ilaborate classification of mountain glaciers (p. 42), 

 )ased partly upon comparative alimentation, is not, 

 lowever, likely to be generally adopted ; most of the 

 'types" are necessarily nothing more than phases 

 vhich merge together indefinitely both in space and 

 ime-relation. 



With respect to the long controversy as to the 

 lotency of ice as an eroding agent, Prof. Hobbs in his 

 reface explicitly disclaims any intention to deal with 

 'the views of that school of British geologists par- 

 icularly which holds, that the denudational effect of 

 [lacier ice is negative." So he does not refer to these 

 lews in adopting alternative explanations of the 

 rltical phenomena; e.g. the "Cascade Stairway" and 

 he "Hanging Valley," in chapter iv. In this con- 

 ection it may be remarked, though not mentioned by 

 tie author, that the long trench-like valleys by which 

 le great glaciers pour down to the ice-plain of the 

 tarrier from the high Antarctic plateau can scarcely 

 e assigned to any other cause than ice-erosion. 



In discussing the relation of mountain-form to 

 laciation, Prof. Hobbs dwells with particular 

 Il^)ha6is upon cirque-development, which he believes 

 NO. 2194, VOL. 88] 



to have a greater importance than has been generally 

 recognised; and in this branch he takes upon himself 

 the role of special pleader. For the initiation of a 

 cirque through the agency of a snow-bank, he calls 

 in the process of "nivation," i.e. selective perishing of 

 contiguous moistened rock, as first suggested by Mr. 

 F. E. Matthes from his observations in the Bighorn 

 Mountains of Wyoming. In the later development of 

 the cirque, the berg-schrund is considered to be a 

 prime factor by the author, who has been duly — 

 possibly even unduly — Impressed by results rf Mr. 

 W. D. Johnson's celebrated exploration of the berr- 

 schrund of Mount Lyell glacier, C.ili nrnl-i, where ''-'■ 

 sapping of a perpendicular wall of rock was fornd to 

 be in progress at the bottom of the fissure. The basis 

 of observation is so limited that it may legitimately 

 be questioned whether this sapping effect is general. 

 However, the author considers that cirque recession 

 is mainly responsible for the residual topographical 

 forms of most high mountains, and he illustrates the 

 progressive stages by good examples from western 

 U.S.A., stating that "in parts of Europe, and in the 

 Alps in particular, one looks in vain for evidences of 

 the earlier and more significant stages," owing to the 

 more prolonged and vigorous glaciation. 



In final chapters the meteorological conditions of 

 existing ice-sheets are summarised, and it is considered 

 that the strong radial winds of Greenland and the 

 Antarctic are due to the sliding outward of chilled 

 air along the surface of the ice-dome. 



The author fully recognises in other parts of his 

 work the proved aridity of both polar areas, but 

 passages on pp. 42-3 and loo-i are likely to give the 

 erroneous impression that the ice-caps are areas of 

 heavy precipitation. At p. 238 there is an obvious 

 misprint of Arctic for Antarctic. 



Independently of the author's opinions on debatable 

 matters, which may or may not be acceptable, every 

 geographer and geologist interested in ice will appreciate 

 these clear descriptions and excellent illustrations of 

 the earth's great glaciers — they make up into a 

 most presentable book. G. W. L. 



PRECESSION AND PARADOX. 



Draysonia : being an Attempt to Explain and Popu- 

 larise the System of the Second Rotation of the 

 Earth, as Discovered by the late Major-General 

 A. W. Dray son; also giving the Probable Date and 

 Duration of the Last Glacial Period, and Furnishing 

 General Drayson's Data, from which any Person of 

 Ordinary Mathematical Ability is Enabled to Cal- 

 culate the Obliquity of the Ecliptic, the Precession 

 of the Equinoxes, and the Right Ascension and 

 Declination of the Fixed Stars for any Year, Past, 

 Present, or Future. By Admiral Sir A. F. R. de 

 Horsey, K.C.B. Pp. 1x4-76 + diagram. (London : 

 Longmans, Green, and Co., 191 1.) Price 3s. 6d. 

 net. 



C^'ENERAL DR.WSON'S book on the "Motion of 

 ^ the Fixed Stars " is not a model of lucidity and 

 generally fails to convince those who endeavour to 

 grasp its argument. It was, therefore, most desir- 



