Mr Buchanan on the Strength of Materials, 157 
heavy drag, which causes a very material deduction from the 
working power, so that, on this account, these machines have not 
yet been brought into general use. At present, indeed, they 
can only be viewed as the first rude attempt at the invention 
of the steam-carriage, which, sooner or later, (and, to all appear- 
ance, the period is not distant), must become the general vehicle 
of communication between different places. They resemble the 
huge and ponderous machines first introduced in this country 
as travelling carriages, and must speedily be superseded by an 
improved mechanism, more akin to the light, yet secure, vehicles 
now in use. The improvement of these machines involves an- 
other branch of the subject, which opens yet a new and exten- 
sive field for inquiry ; namely, the construction of steam-boilers, 
in which strength is no doubt indispensable; but in which, also, 
lightness is in many cases an essential requisite. This object be- 
comes of still greater moment, from the numerous failures which 
have taken place, and the dreadful consequences to which they 
have led. But these accidents have, in many cases, arisen, not so 
much from any deficiency of strength, or thickness of matter in 
the boiler, as from a want of that due and proper disposition of it, 
on which, as already remarked, strength often depends, as much 
as on mere material. 
Numerous other examples of the same kind might be ad- 
duced of the importance of this subject ; and into whatever 
department, indeed, of practical mechanices we look, we find 
such new and striking proofs of its utility, that it becomes 
an object, interesting not merely to the engineer and mecha- 
nic, but to the public at large : For, consider, even in point 
of economy, what an immense saving has arisen, in consequence 
of the improved knowledge on this subject which distinguish- 
es the present age. Were our houses, our bridges, and the nu- 
merous other works of domestic and of public economy, which 
are required in this great community of industry and wealth, 
—were these to be all executed on the ancient models, what 
a waste of capital would not this occasion ; and what a saving, on 
the other hand, may we not look for, by continuing to follow 
out the same principles, and to improve upon their application 
Our buildings may be in many cases as expensive as before, but 
they are more convenient and luxurious, and this amounts obvi- 
