The magnitude of the stresses in built-up cylinders is determined by
calculation, on the presumption that initial stresses do not exist in
the respective layers of the tube and of the hoops which make up the
walls of the cylinder. Nevertheless, Rodman, as early as the year 1857,
first drew attention to the fact that when metal is cast and then
cooled, under certain conditions, internal stresses are necessarily
developed; and these considerations led him, in the manufacture of cast
iron guns, to cool the bore with water and to heat the outside of the
moulds after casting. Although Rodman's method was adopted everywhere,
yet up to the present time no experiments of importance have been made
with the view of investigating the internal stresses which he had drawn
attention to, and in the transition from cast iron to steel guns the
question has been persistently shelved, and has only very lately
attracted serious attention. With the aid of the accepted theory
relating to the internal stresses in the metal of hooped guns, we can
form a clear idea of the most advantageous character for them to assume
both in homogeneous and in built-up hollow cylinders. In proof of this,
we can adduce the labors of Colonels Pashkevitch and Duchene, the former
of whom published an account of his investigations in the _Artillery
Journal_ for 1884--St.
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