38o NATURAL SCIENCE. May, 



He showed, for example — and Kendall's recent study of the sections 

 exposed by the Manchester Ship Canal support it — that the old view 

 of the three-fold classification of the drift into an upper and a lower 

 boulder clay, separated by sands, is absolutely untenable ; that 

 even within very short distances this supposed sequence is often 

 reversed, and we may get the boulder clay in the middle, with sands 

 above and below. A second point of great importance was his insis- 

 tence on the influence of water in depositing and arranging the glacial 

 materials : it may act in the form of subglacial streams or lakes, 

 which are either upon or in front of the glacier. Probably, however. 

 Professor Lewis's most important contribution to British geology has 

 been the practical annihilation of the theory of the submergence of 

 England to the depth of 1,400 feet in an interglacial period. This 

 theory he once characterised as " the most pernicious one ever pro- 

 pounded in geology " (p. 375), and against it he never ceased to wage 

 war. That probably not one of the younger English geologists now 

 believes this theory is, practically, entirely owing to the work of 

 Professor Lewis. To have laid this bogey was itself a most brilliant 

 achievement. 



There are a few points, however, in which Professor Lewis seems 

 to have overstated his case. Thus his law that "every glacier is 

 bounded by a terminal moraine," is not likely to be generally 

 accepted ; it was founded at the time when it was confidently 

 expected that the moraines of the Eastern States of America would 

 be found to extend right across the Central Plain and unite with the 

 old moraines of the Rockies. But now that it has been proved that 

 this is not the case, and that the extra-morainic fringe is more exten- 

 sive that was once thought, this view cannot be accepted as Professor 

 Lewis stated it. A still more important point was his former denial 

 of the existence of more than one glaciation, and his refusal to 

 admit the action of land-ice for the Essex Boulder Clay, which 

 was a natural corollary from the former. His examination, however, 

 of the Frankley Hill sections convinced him that there have been 

 two glaciations, and that his " terminal moraines " were all formed in 

 the later. It is, therefore, highly probable that if he had examined 

 some of the Essex sections after this, he would have accepted the 

 Boulder Clay there as a true till belonging to the earlier glaciation ; 

 he would not then have attributed it to an extra-morainic lake, though 

 the glacial gravels of this district are probably formed by some 

 such agency. It is impossible to regard the scattered denuded 

 remnants of the South Essex Boulder Clay as synchronous with 

 the comparatively unweathered moraines of the Lake District and 

 Wales. The acceptance of a double glaciation removes the most 

 serious of the objections to Professor Lewis's hypothesis. 



The volume is well printed, and has been most carefully edited. 

 The explanations and notes of Dr. Crosskey and Mrs. Lewis, and a 

 valuable appendix by Mr. Kendal, strengthen and remove doubts from 

 Professor Lewis's position. The maps and sketches are clear and 

 instructive, though some improvements might easily have been made 

 in some of the former that would have made them more in 

 accordance both with the facts and Professor Lewis's theories. 

 Had a few such alterations been made, they would have been of more 

 service. The only two serious regrets we feel are, that there is no 

 index — the list of contents is, however, a full one — and that the volume 

 has not been adorned with a portrait of its author. 



J. W. G. 



