340 
MINUTES OF PROCEEDINGS OF 
With respect to theory it may be urged in its favour, in the first place, 
that a forged breech-piece (which is a comparatively expensive article and 
liable moreover to fly into fragments should the gun burst) is not required 
with a solid-ended steel barrel and long thick coils, although it is absolutely 
necessary with several short coils to compensate for the longitudinal weak¬ 
ness of their several joints. And in the second place, that if a series of thin 
coils help us to distribute equally the induced strain on a gun by shrinking 
on each coil separately, the method is open to the serious objection that it 
is practically difficult to calculate the respective proportionate amount of 
tension, and consequently the greater the number of pieces in a gun, the 
more likely some weakness will exist in the mass owing to the undue strain 
on some of the parts; for instance, a 13-inch gun of original construction, 
(Experimental No. 300), split some of its outer coils while the interior ones 
remained uninjured, thus clearly proving that there was too great strain 
on the former. Shrinking on the coils successively was adopted by Sir 
William Armstrong as a convenient mode of adhesion and not on the 
distribution theory, which was subsequently enunciated. In the formation 
of a triple coil it is generally a manufacturing necessity to have the first 
coil cold before the second bar is wound on, but the third bar is wound on 
while the second coil is hot; the second and third layers therefore cool and 
contract simultaneously, and are kept in a state of tension by the first which 
they compress to a certain degree. So here also the theory may be carried 
out, for assuming that iron expands irrespective of its density the three 
layers could not recover their natural condition on subsequent heatings. 
Thus far for theory, but practical men will be glad to learn that searching 
and comprehensive experiments have taken place with guns on the new or 
present service construction, and that the results show beyond all doubt 
that it is as strong, if not stronger, than its original type. 
These experiments, together with the details of the present construction 
of our heavy guns, will be described in a future number. 
