386 Notices of Books. (July, 
Elements of Practical Construction for the Use of Students in 
Engineering and Architecture. Part I. By SAamMuEL 
Downinc, LL.D. London: Longmans and Co. 
Tuis is another work by the same author as the above, and is 
noticeable on account of the great care and precision with which 
it has been compiled. In this volume the resistance of mate- 
rials to direct compression and tension only is treated, leaving 
to another volume the subjects of elasticity, indireét compression 
and tension, transverse resistance and torsion, &c. It must be 
clear to every one interested in the subject of construction how 
very important it is that the real strength of materials employed 
should be perfectly understood, and that they should know how 
to calculate the factor of safety under varying circumstances. 
This is more difficult when varying or transverse strains have to 
be allowed for, but should be comparatively easy in the case of 
direct compression and tension only. These latter may gene- 
rally be classified under four heads, viz.—First, the resistance to 
direct extension ; a force being in action tending to tear asunder 
the fibres or particles of the body, as is the case in tie-rods, the 
links of the main chains of a suspension bridge, chain cables, 
screw-bolts, &c. Second, the resistance to direct compression ; 
a force being present tending to crush the particles or fibres, as 
in pillars, piers of bridges, shafts of columns, &c. Third, the 
resistance of a beam supported at one or both extremities to a 
force acting in a direction transverse to its length, and in fibrous 
material, as wrought-iron and timber, perpendicular to the line 
of fibres, which force is illustrated in the girders of bridges, 
beams, &c. Fourth, the resistance to forces of torsion which 
act so as to twist the fibres, as in crank-axles, the shafting of 
machinery, capstans, &c. Besides the above, all of which are 
clearly dealt with in the present volume, many other complicated 
varieties in the mode of action of the resisting powers of bodies 
may be enumerated, such as that which takes place from the in- 
terior to the exterior surface of hydraulic presses, and of pieces 
of ordnance when fired, and so forth, to which some reference 
also is made in Mr. Downing’s book. The principle upon which 
this work is based is that first giving a proposition for treating 
each material, stating its average ultimate resistance: this is 
followed by experimental proofs, and then are given illustrations 
of the material so strained, taken from completed and successful 
structures of eminent engineers. 
The publication is a very valuable one, and seems especially 
adapted for the purpose for which it is primarily intended, namely, 
for the use of students, to whom we can confidently commend 
it for study, whilst it will, no doubt, also prove valuable for 
reference by those engaged in practical work. 
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