422 



NA TURE 



[August 30, 1S94 



Stanford's), should all deviate little from the 400-feet 

 contour line. 



The volume is full of minute observations and acute 

 remarks. Readers will lind many cherished beliefs 

 rudely handled ; perhaps may feel some of them shaken. 

 What a heresy is his denial of the three-fold division of the 

 Drift. In disbelief of interglacial periods he has had pre- 

 decessors. Herr Penck will find the assertion that fre- 

 quent and finely striated stones in a clay are an argument 

 against that clay being ground-moraine. Neither con- 

 tortions nor groovings are here invariably ascribed 

 to a glacier ; on the contrary, he explains most 

 such when they occur as products of his lakes or his 

 moraines. He has seen no evidence (in Switzerland) 

 for glacier excavation of lakes). He expresses opinions 

 freely and forcibly : it is refreshing to read that " much 

 rubbish has been written on the Cromer clitTs." The 

 doctrine of a post-pliocene great marine submergence he 

 believes " the most pernicious one ever propounded in 

 geology.'' Amusing is his description of the " remark- 

 able properties of this sea, wholly unlike any known sea. 

 It made till and eroded till : it filled some regions with 

 drift, while others it cleared utterly of all drift; its ice- 

 bergs made stria;, while its waters washed them away.' 

 It is true that like language might be applied to the 

 effects of glaciers, as described by some of theiradmirers. 

 Probably it did not occur to him that with regard to them 

 any expression of opinion was needed. 



The author's own views offer points for an opponent's 

 attack. While he cannot induce himself to believe in a 

 thousand feet of submergence, it seems to him simple 

 for Scotch ice to have climbed a thousand feet up a j 

 Welsh hill, and easy for it to have pushed por- : 

 tions of the sea-bottom to the top. He repeatedly . 

 distinguishes between clay formed under a glacier (till) 1 

 and clay formed in a glacier lake (boulder-clay). But 

 when he sees only till at Filey, and only boulder-clay in 

 East .-Vnglia, it is not easy to make out which of their 

 points of difference are the critical ones. He makes 

 several references to stria; as indicating direction of 

 ice-motion. Yet his ultimate conclusion appears to be 

 that the shape of the striic depends only on the slope of 

 the rock, and, except on level ground, gives no guide to 

 the direction of motion. He frequently insists on the 

 effects of great floods and debacles which would result 

 from his glacier-dam lakes, but he does not indicate the 

 way in which these catastrophes would be brought about. 

 "1 believe," he says, "that the Scandinavian ice-sheet 

 would temporarily dam up the I lumber and form a great 

 inland lake, which would pour over the country to the 



south in debacles, making gravels " The water 



would rise steadily to a level of overflow, but how would 

 a dc'bacic be thereby produced .' Such floods seem no 

 necessary part of his theory ; however, his belief in them 

 is firm. 



To decipher field notes intended only for the writer's 

 own eye, must have been a most difficult task. It has 

 been performed with remarkable success : of course, 

 mistakes have not entirely been avoided, but probably 

 each will be obvious to and easily corrected by any reader 

 who is concerned with the case. In the illustrations on 

 pages 322-4, some clays are marked " Permian." There 

 is no Permian clay in that neighbourhood ; the word 

 No. 1296, VCL. 50] 



should evidently be Pennine, a designation for a division 

 of the Midland boulder-clay. 



Prof Carvill Lewis began his studies in Pennsylvania, 

 and there obtained his conceptions of moraines as 

 '• high-tide marks" for glaciers. He came to the British 

 Isles for explanations of phenomena which perplexed 

 him in America. In Ireland he sought and thought he 

 found a solution of Transatlantic problems. He ex- 

 tended his researches over England and Scotland, and 

 visited the Alps to see existing glaciers. The ideal order 

 of study would be to begin by learning all about ice, and 

 then applying the acquired knowledge to these questions. 

 But practically all, even Carvill Lewis, begin upon de- 

 posits said to be glacial, though all do not goon to examine 

 actual ice ; and very few can study its grandest manifest- 

 ations. It is much to be wished that such a geologist as 

 he could spend some summers and winters round Green- 

 land and Hudson's Bay. If to this he could add an 

 acquaintance with Antarctic ice, he would have an equip- 

 ment of appropriate knowledge such as no one has yet 

 brought to bear on the question. Vet even so there is, 

 perhaps, no spot on the earth where we can now see a 

 glacier advancing across unglaciated lands : a cause 

 whose effect is freely invoked by various writers on 

 this question. However, we must use as best we can 

 such means as we possess. Two characteristics of 

 Carvill Lewis seem especially worthy of our imitation, viz., 

 his untiring assiduity — we are told that he traversed the 

 country between Cork and Mallow six separate times ; and 

 his readiness to acknowledge mistake and correct it — 

 he completely retracts more than one opinion at first 

 freely expressed. If any critic had condemned this as 

 " a complete change of front," he would probably have 

 answered, " I am ready to front any way where I see a 

 road to truth." 



An estimate of the advance which this book will have 

 made towards a full and true theory is only possible to 

 an infallible critic. His idea, that there ought to be a 

 definite mark of the furthest extension of a glacier, seems 

 to me a correct one : if so, such marks should be sought 

 for. His clear conception of the power and .action of 

 floating ice deserves to be studied and developed. His 

 distinctions between the products beneath an ice-sheet 

 (till), adjacent to an ice-sheet (moraine), beyond the ice- 

 sheet, but in waters washing it (boulder clay), are real 

 distinctions of the highest importance. Surely there must 

 be criteria of difference, whether the author has arrived 

 at them or not Surely when such criteria are ascer- 

 tained, we shall be very near the solution of one side of 

 the glacial problem. Still would remain for study another 

 side : What brought that problem into existence ; what 



was really the cause of the Ice Age? 



E. Hi 1.1.. 



UNIVERSITY EXTEXSJON. j 



Aspects of Modern Study. Pp. 1S7. (London : Mac- 



millan and Co., 1 894.) 

 •■"pHlS volume consists of addresses delivered by Lord 

 1 Playfair, Sir James Paget, Prof. Max .Muller, the j 

 Duke of Argyll, and Canon Browne, among others, to j 

 students of the London Society for the Extension of 

 University Teaching, at annu.al meetings held at th 



