554 



NATURE 



[October 5, 1905 



believe in the old men rather than in the new." It 

 is true that in these cases he is referring to special 

 points, but again and again one cannot but feel in 

 reading the book that the writer pavs undue regard 

 for authority, without considering that his " old 

 masters " were not acquainted with all the facts 

 which we now possess, and that they themselves 

 changed their views. Sedgwick, for instance, came 

 to believe in an Ice age. Moreover, if these were old 

 masters, so were Hutton and Playfair, Lyell and 

 Buckland, whose views are not always so palatable 

 to the author. It may be remarked, also, that a 

 knowledge of mathematics and physics was not con- 

 fined to the geologists of those days. One of the 

 most ardent of the existing advocates of ice-erosion, 

 concerning whose paper on ice action in Skj'e {Trans. 

 Roy. Soc. Edit!., vol. xl., iqoi) Sir Henry is silent 

 in these two volumes, was a high wrangler, and took 

 a first class in physics at Cambridge. 



The theory of an Ice age was largely put forward 

 owing to the existence of rounded and striated rock- 

 surfaces and scratched and polished boulders. These 

 resemble similar productions of modern ice to such a 

 degree that the geologist has no more hesitation 

 in referring them to ice-action than he has to assign 

 the formation of the pebbles of a river to stream- 

 action. The inference drawn from the existence of 

 these phenomena has been supported by a host of 

 other observations, biological as well as physical, and 

 if Sir Henry should succeed in disproving the exist- 

 ence of an Ice age he will also break down the 

 essential principle of geology, " that like effects imply 

 like causes." 



It would be impossible in a brief article to discuss 

 all the questions raised in this part of the work. 

 We must content ourselves with a few observations. 

 Though reference is made now and again to the 

 Greenland ice and to the ice masses of Spitsbergen, 

 it is the glaciers of the alpine type to which most 

 frequent appeal is made. To this we shall recur, 

 but in the meanwhile would invite the author's atten- 

 tion to yet another treatise concerning which he is 

 silent, where another type of ice work is described, 

 namely, I. C. Russell's volume on the Malaspina 

 Glacier (thirteenth annual report of the U.S. Geo- 

 logical Survey). 



When describing the Till or Boulder-clay, the 

 author quotes a description of it by Prof. James 

 Geikie, and goes on to observe, " tliis being with- 

 out question the most typical of so-called glacial de- 

 posit, it is a remarkable fact that no such deposit 

 is now being made, so far as we know, by land-ice 

 anywhere." He must have overlooked a passage in 

 a paper to which he elsewhere refers, by Messrs. 

 Garwood and Gregory, on the glacial geology of 

 Spitsbergen (Quart. Joiirii. Geol. Soc, vol. liv.). 

 They say : — 



" On the broad plain at the foot of Booming Glacier 

 we found some square miles of a tough mud con- 

 taining boulders and pebbles; it only needed to be 

 dried and hardened to form an ideal Boulder Clay. 

 Clearly this deposit had been laid down by land- 

 ice." 



NO. 1875, VOL. 72] 



The author objects to the sharp line which is drawn 

 by many geologists to show the margin of the ice 

 at its period of maximum extension, and denies the 

 existence of anv evidence for this, arguing that the 

 Boulder-clay, the masses of gravel and loam, and 

 the loess are genetically connected. Of this we shall 

 doubtless hear more when the third volume appears. 



Much is naturally made of the conflict of opinion 

 among geologists concerning the occurrence of inter- 

 Glacial periods, and the relative importance of land- 

 ice and floating-ice in producing the phenomena 

 generally taken to indicate the occurrence of a Glacial 

 period. These questions are certainly not settled to 

 everyone's satisfaction, but they in no way invalidate 

 the conclusions which have been drawn as to the 

 existence of an Ice age. 



Though we do not agree with the author in his 

 main conclusions put forward in this section of the 

 work, we must admit that much that he writes is 

 worthy of consideration, even though his views seem 

 exaggerated. For instance, he argues that much of 

 the material forming the drifts was broken up prior 

 to the so-called Ice age, and this w^e believe to be 

 true, even though the breakage did not occur in the 

 manner advocated elsewhere by the author; but if 

 true, it invalidates the appeal to modern Alpine 

 glaciers to prove the inadequacy of ice as an erosive 

 agent. The loose materials ready to hand at the 

 beginning of Glacial times would supply the ice with 

 the tools for rasping and grinding. As that material 

 became comminuted, unless new material was sup- 

 plied in abundance, the ice would become less 

 effective as an eroder. Also ice, like water, has a 

 base line of erosion beneath which it cannot work. 

 This line may have been reached in the case of 

 .•\lpine glaciers, and the supply of material to the sole 

 have been also largely diminished, in which case one 

 can no more argue from what Alpine glaciers are 

 now doing as to the effects of land ice in the Glacial 

 period than one can explain the cafions of the 

 Colorado by reference to a little stream which has 

 established its base level. 



Throughout the work much has been made of the 

 conflicting views of geologists as to the details of 

 ice action. Sir Henry is obviously greatly impressed 

 with the fact that in the long and arduous attempt 

 to unravel the Gordian knot the skein sometimes 

 seems to have become hopelessly twisted; but he who 

 carefully studies the process of disentanglement sees 

 that, notwithstanding the many kinks, the tangle is 

 becoming less. The author, impatient of the slow 

 process, has elsewhere attempted to cut the knot, and 

 will evidently give reasons for this act in the third 

 volume. We fear that the attempt will not be re- 

 garded as successful, either by the " ultra-glacialists " 

 or by geologists in general. 



We cannot recommend the book to geological babes 

 and sucklings, but it will well repay perusal by the 

 advanced reader. He will forgive the " energetic 

 adjectives and adverbs," which are hardly necessary 

 to a calm and dispassionate discussion, on reading 

 the author's frank apology in the preface. Tlie store 

 of facts collected in the book is of the utmost value 



