84 Reviews—The Data of Geochemistry. 
as Dana, Davis, and, Daly, whose work affords strong support to 
Darwin’s theory of submergence. 
A chapter on ore deposits has been rewritten by Mr. Rastall. 
The study of ores is a branch of petrology, and a scientific 
classification of ore deposits must be based ultimately upon their 
mode of origin. We may recognize primary ores, vein deposits, 
cavity fillings, replacement deposits, and sedimentary ore deposits 
besides those formed by metamorphic action. 
An interesting section on the history of igneous activity in the 
British Isles is also contributed by the above-named writer as a 
supplement to Mr. Lake’s précis of the geological history of the 
British Isles. Earth movements and igneous activity are so closely 
interrelated that it is impossible to consider them apart. In an area 
like North Wales, for example, where post-Carboniferous movements 
are pronounced, it 1s important to realize that although no igneous 
rocks ascribed to that period are visible, such rocks may nevertheless 
underlie a large part of the district. A map of the chief folds and 
faults of Northern England and Wales is given in plate xxiv. 
The classification of the Permo-Trias of Cumberland and the Vale 
of Eden does not appear to be satisfactory. In the first place 
gypseous shales and marls apparently occur in the top of the so- 
called Permian of the Vale of Eden, as well as in the bottom of the 
Trias. Again, no mention is made of the Keuper Kirklinton Sand- 
stone, which is asserted by Professor J. W. Gregory to overlie directly 
the St. Bees Sandstone, not only of Northern and Western Cumber- 
land, but also of the Isle of Man. These are minor details, however ; 
a wider question is involved in the consideration whether any clear- 
cut division can be established between the so-called Permian and 
Trias in Western Cumberland. 
As regards the general direction of travel of glacial erraties, it 
may be mentioned that a boulder of Shap Granite was found by the 
writer at Bledworth in Nottinghamshire, far south of the limits shown 
in the map, fig. 34. 
The book is well illustrated, printed in clear, readable type, and 
furnished with a useful index. 
Bass: 
. Tue Data or GEocHEMIsTRY. By F. W. Cuarke. Fourth edition. 
Bulletin 695, U.S. Geol. Survey. 832 pp. 1920. 
Wt are glad to welcome the appearance of the fourth edition of 
this invaluable work, which exceeds its predecessor in size 
by about ten pages. In the absence of any prefatory remarks it is 
difficult to obtain any idea of the extent of the changes in a book 
of this size and nature, but a casual examination and an inspection 
of the footnotes and index show that a large amount of the most 
recent work has been noticed. This book has always been remarkable 
not only for the skill with which a vast amount of information has 
been compressed into a comparatively small space, but also for the 
