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Art. XXI. — Remarks on the Strength of Materials ^ with an 
Account of several Experiments on the Transverse Strength 
of Wood and Iron. By George Buchanan, Esq. Civil En- 
gineer, Edinburgh. 
-The subject of the strength of materials forms a very inte- 
resting branch of mechanics, and the importance of which can- 
not be rated too highly, when we consider its numerous applica- 
tions in the arts, and that, without a correct knowledge of it, 
no one could erect, with success, any structure, either of or- 
nament or utility any work of strength, civil or military ; any 
engine or machine, or, in short, any of those infinite diver- 
sities of form and combination, into which our materials are 
wrought, for the uses of a civilized community. These works 
cannot, any of them, be put together at random ; they require 
contrivance, to enable them to withstand the various strains and 
shocks to which they are continually exposed ; and without a 
knowledge of tlie principles which regulate the strength of diffe- 
rent materials, and even of the same material under different 
circumstances, it would be impossible to construct them, so as to 
preserve, in every part, a strength and solidity proportioned to 
the strain which each has^to bear. 
The construction of our dwelling-houses, for example, illus- 
trates the application of these principles ; and the modern im- 
provements, in the form of their walls, their floors, and their 
roofs, shews the importance of acting on them with judgment. 
Ignorant of the true measure of strength, our architects were 
formerly content to obtain security, by a lavish expenditure of 
materials, and, consequently, also of workmanship. We are 
now equally secure ; but how greatly have we gained, in econo- 
my and convenience, by reducing the thickness of our walls, re- 
ducing the breadth, and adding rather to the depth of the joists 
for flooring ; and by improving, in similar respects, the struc- 
ture of our roofs. Nor does a heavy weight of matter, by any 
means, contribute to secure us from accidents ; on the contrary, 
it often proves the very source of failure, by the undue strains 
which it occasions on the weaker parts of the structure ; the 
strength of which often depends, not so much on the mere mass 
of its materials, as on their skilful disposition, and the due pro- 
