4 FEBRUARY 22, 1917 | 
earlier edition. Chapters on the overfall and 
arched types of dam have been added, and an 
excellent series of cross-sections of typical 
masonry dams, arranged chronologically, forms 
an appendix. The method of analysis followed 
is that due to Wegmann, used for the first time 
in connection with the design of the new Croton 
dam. The authors have amplified the analysis 
_ by a consideration of the uplift due to water 
_ penetrating the foundations or the horizontal 
_ joints of the masonry, and also by taking into ac- 
_ count the ice-thrust exerted against the up-stream 
_ face of the dam when the reservoir is frozen over. 
_ The latter portion of the book is devoted to ihe 
_ problems of tension in the vertical sections near 
_ the toe, to which attention was first directed 
by L. W. Atcherly. Appendices i. and ii. con- 
tain the mathematical theory of arch dams. ‘The 
_ book is one which should occupy a place in the 
library of all designers of masonry dams, 
(4) Probably one of the most difficult problems 
which the engineering designer has to face is 
that concerned with the pressures which may 
exist at the back of retaining walls. Many 
mathematical theories have been evolved which 
assist materially in solving the problem, but the 
infinite variety of physical conditions met with 
in the earth’s crust render exact calculations im- 
possible in many cases. This difficulty is un- 
doubtedly responsible for the comparatively small 
- amount of experimental work available. The 
book on earth pressures just issued by the pro- 
fessor of mathematics in the University of North 
Carolina deals with the theory of soil pressures, 
covering a. wide range of physical properties of 
earth, from those of Rankine, where the soil is 
assumed to be devoid of cohesion and subjected 
to no other external force than its own weight, 
to cases where surcharging and cohesion are 
taken into account. 
Both analytical and graphical methods are em- 
ployed, and the work is comprehensive in scope. 
The last chapter is devoted to a consideration of 
bin theory, the ordinary hopper-bin containing 
coal or ore and the deep bin such as those met 
with in grain silos being dealt with in an adequate 
manner. Thestresses in wedge-shaped reinforced- 
concrete bins, such as occur frequently in the 
toes, heels, and counterforts of retaining walls, 
form the subject of an appendix, whilst some 
experiments made by the author on model retain- 
ing walls at the limit of stability are dealt with in 
Appendix ii. The book well repays the reader. 
It ought to serve a useful end. 
THE GEOLOGY AND SUPPLY OF MINERAL 
OIL. 
Principles of Oil and Gas Production. By Prof. 
B. H. Johnson and L. G. Huntley. Pp. 
XV +371... (New York: John Wiley and Sons, 
Inc.; London: Chapman and Hall, Ltd., 1916.) 
Price 16s. net. 
HIS book should be of especial usefulness 
owing to its combination of practical in- 
formation, including branches of the subject not 
NO. 2469, VOL. 98] 
‘NATURE 
487 
usually considered in general text-books on oil-* 
mining, and its clear and accurate statements of 
scientific principles. The twenty-three chapters 
may be divided into three groups: the first is 
devoted to the chemistry, physical qualities, and 
geology of oil and natural gas; the second 
includes eleven chapters on the development and 
management of oil and gas wells; and the 
third, consisting of one chapter which occupies 
nearly a third of the book, gives a most useful 
summary of existing knowledge of the oil and gas 
fields of North America. 
The most striking feature of the first division 
of the work is its clear expression of the reaction 
from the school which held that the one deter- 
mining factor in oil geology is the folding of the 
beds. It is no doubt true that the folding has 
often largely determined the distribution of the 
oil, and is the best guide in the economic develop- 
ment of the field. There are, however, numerous 
cases in which the rocks are not folded, yet the 
concentration of the oil into pools is due to the 
factors which elsewhere drove it into the arches 
of the folds. The authors therefore devote especial 
attention to the texture of the beds, to the varia- 
tion in the range of those most suitable for oil 
storage, and to the forces which have compressed 
the oil into pools. The authors discuss the origin 
of mineral oil, and firmly reject the inorganic 
theories. They recognise the wide range of oil 
throughout geological time, but that Cambrian 
and pre-Cambrian rocks are unlikely to contain it 
in commercial quantities. . Important oilfields occur 
in the Ordovician and in all later systems. 
In an interesting chapter on folds the authors 
urge more general agreement in the meanings of 
the terms ‘“homocline ” and “monocline,” and set 
a good example of concession, as Prof. Johnson 
abandons his previously advocated use of “mono- 
cline” for beds with a uniform dip in one direc- 
tion. He now accepts Daly’s term “homocline ” 
for a bed with one dip, and “monocline” in its 
more familiar sense for a one-limbed fold. Hori- 
zontal beds the authors describe as “aclines’’—a 
perhaps unnecessary term. They introduce 
the term “chute” for the pitch of a minor 
fold, which is very different from its usual 
use in mining geology. The chapter on the laws 
and leasing of oil lands appears to be a clear 
synopsis of the American law; it quietly explains 
how to avoid by suitable terminology the legal 
decision that the oil or gas under a tract of land 
cannot be sold. They point out, too, that the oil 
and gas industries are hampered by anti-trust 
laws, which in some cases prevent reasonable 
economic co-operation and necessitate wasteful 
expenditure. 
Perhaps the most valuable section of the book 
is the description of the oilfields of North America. 
It is illustrated by an excellent geological map of 
the continent and numerous diagrams of the special 
fields. The literature on them appears well up 
to date. The authors describe the fields, ranging 
from that of Lima-Indiana, which is unique as 
yielding its produce from Ordovician beds, to the 
still more remarkable oilfield among the salt- 
