380 Reviews—The Study of Geological Maps. 
Tue Stupy or GrotocicaL Maps. By Grerrrupe L. Exiss, D.Sc., 
Fellow of Newnham College, Cambridge. pp. 74, with 7 plates 
and 64 figures. Cambridge University Press. 12s. net. 
EOLOGISTS and teachers of geology in England will welcome 
this small book from the pen of so experienced a teacher and 
field worker as Miss Elles, and the more so since, as stated in the 
preface, it is based on lectures given by her for many years to 
honours students in geology, and has therefore been already put 
to the proof. 
The first three chapters are given up to the exposition of 
topographical maps in their relation to geology, and full emphasis 
is given to the paramount importance of surface relief in the analysis 
of geological maps. One would perhaps expect this from an author 
whose work has been chiefly in the more rugged parts of these islands, 
but it is none the less commendable from the fact that such emphasis 
is frequently lacking in other works on geological maps. 
The remainder of the book describes and illustrates methods of 
solving the problems of dip, thickness, relative age of strata, etc., 
from a geological map. ‘The more complicated forms of outcrop 
given by folds, faults, overthrusts, and by igneous rocks are dealt 
with as fully as space permits. The great feature of the book is the 
frequent quotation of examples of the various types of formation 
to be found on the maps of the Geological Survey and the description 
of special areas on those maps. Full use is made of footnotes for 
reference to authorities or maps, so that the private student is 
introduced to the proper literature for fuller study. 
In the solution of the problems recourse is had to the graphic 
methods of Harker, and these are illustrated with diagrams. The 
graphic constructions are dealt with in an appendix to the third 
chapter, and one is inclined to think that it is too condensed for 
the average reader who cannot have the benefit of personal demon- 
stration. Experience leads one to believe that most students of 
geology find more difficulty in solving the problems of solid geometry 
that arise from geological maps than in anything else and a more 
detailed treatment would have added to the value of the book. 
A final chapter on the interpretation of geological maps is excellent 
but all too brief, and tables of symbols and of the ordinary 
trigonometrical functions are added. 
The book is very well illustrated with diagrams, sections, and maps, 
and a series of plates of block diagram drawings helps considerably 
in expounding the relation between surface relief and geological 
phenomena. After the excellence of the text-figures one is somewhat 
surprised to find the folding map at the end to be one of the less 
useful productions of the Ordnance Survey, exhibiting most. 
prominently the two great faults of an irregular contour interval 
and heavy overprinting. The book is strongly bound and almost 
entirely free from printing errors, well up to the standard of the 
other books in the Cambridge Geological series. It is noteworthy, 
