154 
MINUTES OF PROCEEDINGS OF 
wrought-iron for the bore (see Fig. 14). If we take a 32-pr., 
whose internal and external radii are roughly 3 ins. and 10 ins. 
respectively, we have a strength of yh of 7, or 2 ins. of cast-iron. 
But if the internal radius be bored up to 5 ins., and a wrought-iron 
tube 2 ins. thick be put in place of the cast-iron bored out, we have, 
for the strength of the remaining cast-iron, -fa of 5, or 2£ ins. So 
that the cast-iron is actually stronger than it was before. The strength 
of the wrought-iron tube has to be added, so that these guns are 
probably at least twice as strong as they were before conversion for 
circumferential strain. See Fig. 6, where the unshaded portion repre¬ 
sents the strength before conversion. The slightly shaded part repre¬ 
sents the gain by conversion.* 
III. New Proposed Pattern. 
I have now to examine the pattern proposed by myself, and to show 
that it is the system which ought to be adopted for very heavy guns. 
The principle consists in receiving the longitudinal strain on a solid 
block of metal not rigidly connected with the rest of the gun. There 
is thus no longitudinal strain on the gun, and consequently no cross 
strain on the bore. Mr. Eigg^s views are thus perfectly met. Major 
PallisePs maxim is also fully carried out; for, the longitudinal strain 
being entirely removed, it is quite easy to turn our whole attention to 
getting circumferential strength as near the bore as possible. The iron 
can be used in the best possible condition, and under the best form 
of arrangement. I have already noticed that near the bore the coils 
ought to be thin, but that they may increase in thickness towards the 
outside. A reference to Figs. 7 and 15 will show how this is carried out. 
About one-fourth only of the useful effect of the iron is lost. In addi¬ 
tion to this, the iron need not be over-heated. All the coils may be made 
short, and the inner ones could be well hammered, which is a matter of 
great importance. They could even be rolled out like tyres of railway 
wheels. The outer coils, which are thicker, could, without danger, be 
on the side of under-welding rather than over-welding. Their short¬ 
ness would be favourable to perfect manufacture, and at least the two 
ends of each coil would always be sound. No second heating is neces¬ 
sary; so that there would be no tendency to form cavities in the iron, 
or to split into two cylinders. 
Sir William Armstrong last year, in his address as President of the 
Manufacture Institution of Mechanical Engineers, at the Newcastl 
meeting, says :—- 
“ Krupp and Whitworth—both great names in gunnery—though differing widely 
in their views in other points, agree in this, that steel is the right material for the 
entire gun. I, on the other hand, have always advocated wrought-iron in the form 
* The diagram is to he considered as representing strength, and not elasticity. Cast-iron is 
quite as elastic as wrought-iron, or more so; hut it is probable that wrought-iron, owing to its 
malleability, allows the tube to be extended beyond its elastic limits without rupture or great loss 
of strength. 
