Reviews—Dr. J. W. Gregory’s Geology of To-day. 81 
On the contrary hypothesis that these channels were produced by 
the outflowing waters of temporary lakes upheld by an ice-barrier, 
all these phenomena find an explanation, and the lakes themselves 
could in most cases have been predicted from the positions of the 
ice-margins that were deducible from other classes of evidence. 
I do not overlook the fact that there are two fundamentally 
antagonistic explanations of the ‘ Drift’ phenomena—the Land-ice 
theory and the ‘Great Submergence’, but whichever of these 
interpretations be the right one, neither is compatible with the 
‘river-trespass’ hypothesis. On the other hand, I have long thought 
that the study of these ‘‘ certain channels’? did administer the merciful 
and much needed coup de grdce to the ‘Great Submergence’. 
REV Lew s- 
I1.—Groroey or T'o-pay: a popular introduction in simple language. — 
By J. W. Greeory, F.R.S., D.Sc. 8v0; 328 pp., 26 plates. 
London :.Seeley, Service & Co., Ltd., 1915. Price 5s. net. 
HIS is one of a series, ‘‘ The Science of To-day,” intended to be 
at once advanced and popular: advanced in the sense of being 
abreast of the latest facts and theories, popular as being intelligible 
to those unfamiliar with technical modes of expression. ‘‘ Geology,” 
as the author fully recognizes, is a big mouthful; ‘“‘a full digest of 
modern geology would be impossible in the space of a book of this 
size, and it would also be comparatively useless to a general reader.” 
This being so, 1t is surprising that the author or the editor, if there 
be such a person, should have weighted the subject by the inclusion 
of paleontology, by which we do not mean such account of ‘‘ The 
Age of Trilobites”’, ‘‘The Age of Graptolites’’, and so forth, as is 
contained in ‘‘ Part III, Historical Geology’’, but rather the more 
biological aspect of the science that is headed ‘‘The Story of Life on 
Earth” and constitutes Part IV. This could easily and naturally 
have been expanded to form an independent volume in the series, 
thus leaving space for the more adequate treatment of certain strictly 
geological questions, which in the book as it stands are discussed too 
briefly or not at all. For instance, the excellent chapter on the Age 
of the Earth contains no reference to that most fascinating method of 
investigation provided by pleochroic haloes; and, even in such historical 
_ geology as there is, one would have expected a reference to the 
remarkable Middle Cambrian fauna described by Walcott from British 
Columbia and supposed also to have been detected in our own Islands. 
Let it none the less be admitted that if, in ‘‘the round world and 
all that therein is”’, the author has shouldered too Atlantean 
a burden, he has none the less borne it right well. Professor Gregory 
is one of the very few geologists of the present day who has attempted, 
or at least attempted with any success,.to carry on the traditions of 
the heroic age. ‘l'o him the description of a new species of microscopic 
fossil comes as easily as the survey of an unexplored continent; the 
forces that fashion the globe are as familiar to his pen as those that 
determine the shape of a sea-urchin; from Eozoon to Eoliths nihil 
DECADE VI.—VOL. III.—NO. II. 6 
