132 Reviews—The Evolution of a Coast-line. 
depression, as shown by the depth to the rock-floor of some of the 
river mouths. R. Hy R: 
THE Evo.ution or A Coast-Line, BARRow TO ABERYSTWYTH AND 
THE IstE or Man, with Notes on Lost Towns, SUBMARINE 
Discoveries, ETC. By Witiiam ASHTON. pp. i-xiv and 
1-302. London: Edward Stanford. 1920. 
HE author has long been engaged in the study of the features 
presented by the coast-lines considered in this volume, which is 
based upon his former work The Battle of Land and Sea. 
There is, especially in the earlier chapters, a good deal of geological 
matter which is hardly relevant interspersed with information of 
considerable interest. If the story had been written in a more 
connected form it would have saved the reader much trouble. 
Notwithstanding these objections, the book will be found of very 
high value to anyone concerned with the study of the coastal changes 
in the area described, for it is a storehouse of facts, many of which 
are derived from a study of historic documents, including old maps, 
while others are due to the author’s personal observations. 
The author maintains that for some thousands of years subsidence 
has been in progress along the Welsh, Cheshire, and Lancashire 
coasts to a point provisionally fixed somewhere between Fleetwood 
and Barrow-in-Furness, north of which elevation is proceeding. 
The volume is amply illustrated with diagrams, maps, and photo- 
graphs, including a large number of ancient maps of the coastal 
tract. J. KE. M. 
PopuLaR O1L GEoLocy. By Professor Victor ZipcLer. First 
edition, pp. vill + 149, 1918. Second edition, pp. xil (not 
numbered) + 171,1920. New York: John Wiley & Sons, Inc. 
London: Chapman & Hall, Ltd. 
T HE word “ popular ” prefixed to the title of any book purporting 
to deal with a particular branch of Natural Science is usually 
sufficient to deter the average technical man from a perusal of its 
pages. Possibly its use unconsciously reminds us of all the quaintly 
worded phrases and ambiguous paragraphs characteristic of volumes 
written with the intent of making a difficult subject easy, and one 
is inclined, however erroneously, to prejudge and condemn a work 
bearing this superscription. It is given to comparatively few 
scientific men to be able to write a technical treatise which, while 
intelligible to the general public, at the same time satisfies the 
most critical expert; the author of the present work, being 
admittedly one of the “‘ few ”’, is therefore to be congratulated on 
the production of this volume, which fills a very definite space in 
the literature of oil-field technology. 
The book deals only with the general principles of oil geology, and 
does not attempt to go into elaborate detail. The early chapters 
are mainly chemical, and discuss the composition, properties, and 
origin of oil and gas. The succeeding seven chapters are devoted to 
