610 
NATORE 
[AUGUST 13, 1614 
bars become larger than is generally supposed, and 
the resulting bending moments are by no means 
negligible. The theory of the straight stiffening- 
truss based upon the elastic deformation of the 
structure assumes that there is no sensible varia- 
tion from the parabolic form of cable or frame. 
The thermal stresses in_ stiffened suspension 
bridges are discussed. This work should find a 
ready acceptance among engineers and students 
alike. 
(2) It is not surprising that this work has 
reached a third edition in ten years for it possesses 
distinct merit and originality. Unlike the usual 
text-book on tmechanics which is compiled by 
rigid adherence to academic method, it has a 
treatment all its own, and one that will commend 
itself alike to teachers and students who have left 
the abstract for the concrete problems met with 
in practical application. The author asserts that 
it is neither theoretical mechanics on one hand, 
nor applied on the other, since it does not include 
strength of materials, and the reader will not go 
far before discerning a judicious blend between 
the two extremes. The thirteen chapters com- 
prise statics, friction, centre of gravity, rectilinear 
and curvilinear motion, translation and rotation, 
and work, energy, and power. The illustrations 
are clear and essentially represent objects familiar 
to the engineer. 
(3) A short introductory chapter to this volume 
is devoted to the usual thermodynamic relations 
for air and other vapours, after which the various 
types of refrigerating machines and their con- 
struction are described. This is followed by the 
theory of refrigeration and the choice and _ pro- 
perties of refrigerating mediums. We then find 
a chapter on testing refrigerating machines, fol- 
lowed by a discussion on insulation; and finally, 
the various commercial applications are dealt 
with. The discussion on refrigerants has been 
brought up to date by including the work of 
Mollier and others. The descriptions of refrigerat- 
ing plant and methods are very complete. 
(4) A perusal of this work will leave the reader 
in doubt as to the object of the writer, and yet he 
will conclude that it is an interesting and plea- 
santly written essay upon the motives and habits 
of the workman in the pursuit of his work. As 
human nature is the same the world over, it will 
doubtless be found to meet the characteristics of 
the English as well as the American workman, 
and perhaps to suggest to the employer some of 
the causes which have operated to give a nation 
a certain place in the industrial world. To 
American managers who have given the problems 
of works management the 
would and 
NO. 2337; 
a position 
make a 
VOL. 93] 
among 
sciences it appeal, 
direct 
though most men of experience would find their 
views in general accord with those of the author, 
it is pleasant to find them confirmed by one who 
has evidently a clear and shrewd apprehension of 
the actuating forces that underlie all human en- 
deavour. We would however be inclined to say 
ca va sans dire to much that the author has 
written. For instance, few will find fault with the 
statement that inertia is not confined to an inani- 
mate mass and that it has to be overcome in a 
progressive business. Notwithstanding the some- 
what trite remarks that we find throughout the 
work, there is a distinct charm about the manner 
of presentation, and as the author confesses to a 
feeling of incompleteness in the treatment, we 
must take what he has given us with this reserva- 
tion and accept his contribution to a very large 
subject capable of indefinite variation. 
(5) This work on the strength and physical pro- 
perties of bricks, stone, mortar, cement, and 
masonry is a compilation of results of experiments 
with a discussion of the theory of elasticity as 
applied to such materials. The first chapter deals 
with the elastic properties in reference to Hooke’s 
law and Poisson’s ratio for the materials, and 
in the second the behaviour of materials under 
compression is dealt with, which is followed by a 
chapter on the flexure of beams. The ordinary 
tensile tests on various kinds of cement are de- 
scribed and the results tabulated. The strength 
of bricks based upon various experiments made 
by different men is, in view of the variable charac- 
ter of the material, of special interest, also the 
crushing strength of building stones of different 
kinds is given. The chapter on the crushing 
strength of brick piers is of special value as so 
little has been done in this direction, chiefly owing 
to the inherent difficulties of testing and rendering 
the results comparative. The effect of the quality » 
of the bricks and mortar and the workmanship is 
discussed, the results obtained by Popplewell, 
Howard, and others being cited. The thickness of 
the joints, leading dimensions, and other possible 
variations in the test piers make it impossible to 
lay down any absolute laws as the result of the 
tests. The work ought to be of use to engineers 
as a guide to what has been done in a very large 
subject. 
OUR BOOKSHELF. 
Minerals and the Microscope: an Introduction to 
the Study of Petrology. By H. G. Smith. Pp. 
xi+116+xu plates. (London: Thomas Murby 
and @o,, n.d.)» Price 35. 6d. net. 
Tue author of this convenient and systematic little 
treatise is Demonstrator of geology in the Imperial 
College of Science, London, where he has gained 
