THE ROYAL ARTILLERY INSTITUTION. 
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of welded coil for the chief mass of the gun, limiting the use of steel to the internal 
tube, which has abrasion to resist, as well as tensile strain. The expression of my 
opinions upon this point may, probably, not be considered impartial; but I will, 
nevertheless, state the grounds upon which my preference of wrought-iron, thus 
applied, is based. 
“ It has been found both in Elswick and Woolwich guns, that whenever failure 
takes place, it almost invariably originates with that part which is made of steel. It 
is the steel tube which is nearly always the first to crack. So also when the vent- 
pieces, or closing blocks of the breech-loading guns were made of steel, their 
fracture was alarmingly frequent; but since wrought-iron has been substituted, such 
occurrences are rare. The conclusion, therefore, at which I long since arrived, and 
which I still maintain, is that, although steel has much greater tensile strength than 
wrought-iron, it is less adapted to resist concussive strain. This conclusion is in 
strict harmony with the fact that armour-plates made of steel have proved, on every 
occasion of their trial, greatly inferior to plates of wrought-iron. The experiments 
which I made some years ago, on the toughening of steel in large masses by 
immersion, when heated, in oil, led me to expect that this fragility would be 
obviated by that process; and I felt sanguine that I should be able by such 
treatment to produce steel armour-plates of extraordinary resisting power. An 
armour-plate of steel was accordingly manufactured for experiment, and was tem¬ 
pered in a large bath of oil. Its quality was tried by test pieces cut off after tem¬ 
pering, and proved by tension and bending. The result showed a very high tensile 
strength, combined with so much toughness that I was unable to match its bending 
power by any sample of iron I could compare with it. The plate was then sent to 
Portsmouth for trial, in the fullest confidence of its success, but two shots from a 
68-pr. sufficed to break it in various directions, and it was justly pronounced a 
failure. With these experiences before me, it is impossible that I can hold any 
other opinion than that the vibratory action attending excessive concussion is more 
dangerous to steel than iron; and were it not necessary to provide a harder and 
more homogeneous substance than wrought-iron for the surface of the bore, I 
should entirely discard steel from the manufacture of ordnance.” 
I do not wish to trench on the much-vexed Armstrong and Whit¬ 
worth controversy, but in investigating this subject I have arrived at 
a very curious result. Fig. 8 represents my gun made wholly of steel. 
The lower margins of the faintly shaded portions give the strains on 
the gun in its natural state. Above the horizontal line is the tension, 
below the compression. The tension must balance the compression, 
and therefore, on the supposition that within the elastic limits the 
tensile and crushing strengths are equal, the area above the line is 
equal to that below. OA and OA! are the elastic limits of iron; OB 
and OB' of steel. The compression area is necessarily limited, so as 
not to exceed the elastic limits of the metal at the bore. The amount 
of tension must therefore also be limited, and the result is that, when 
the whole are extended, the outer coils are by no means strained to 
their utmost.* If the crushing strain were greater than the tensile 
* Even in the Armstrong gun, with steel tube and wrought-iron coils outside, it is not possible 
to put any great amount of shrinkage in the iron coils; for it is invariably found that at proof the 
steel tube not only becomes diminished in diameter, but also springs forward at the muzzle, thus 
shewing that it has taken up a new position, in which its compression balances the initial tension 
of the wrought-iron coils. The fact that both these guns and the Eraser guns stand heavy firing 
after the steel tube has failed, is thus readily accounted for. 
