THE EOYAL ARTILLEliY INSTITUTION. 
157 
Now, when 3" is a maximum, 
ds 
dt 
2 P 
i.e. } in accordance with the rule laid down by engineers, we can only 
meet half the pressure when it is suddenly applied. 
The Gunpowder Committee gives, with the new gunpowder, the 
maximum pressure in guns of 8 ins. calibre as 15 tons per square inch, 
and not suddenly applied. With a 10-inch gun, the pressure is about 
24 tons. Supposing it, therefore, to be 15 tons suddenly applied, or 
30 tons slowly applied, to cover any margin of error in calculation or 
manufacture, or to allow an extension to heavier guns, the result is that 
a steel gun would be worked up to its elastic limits of 20 tons per 
square inch. Now, it is laid down in engineering, that in no case will 
metal stand 900 vibrations, if worked up to its elastic limits, or one- 
half its breaking strain ; but, if worked up to one-third of its breaking 
strain, 10,000, or even 100,000 vibrations will produce no visible bad 
effects. A wrought-iron tube reduces the diameter of the bore nearly 
one-third, without affecting the useful employment of the steel behind 
it, and the possible effect might be that it would give the necessary safe 
margin within the elastic limits, and thus produce a beneficial effect 
out of all proportion to the reduction of strain which it would cause. 
Taken in connection with the new gunpowder, it might therefore increase 
the endurance even of very heavy guns from 1000 or 2000 rounds to 
10 ,000, or even 100,000, if the bore were renewed so as not to wear out. 
These good results are owing to the great elasticity of wrought- 
iron, which, if used for the bore, not only allows a greater thickness of 
steel to be employed advantageously behind it, and, as a consequence, 
greater initial tension, but also brings into play twice the extra tension 
beyond the initial tension. There seems to be nothing to prevent this 
plan being carried out with heavy guns, if my system of construction 
were adopted; for a hard surface would not be necessary with lead 
coating, and the absence of longitudinal strain would make the welds 
safe. My gun might thus be made a Palliser gun of enormous strength, 
and the amount of steel which it is possible to employ usefully would 
almost make it a Whitworth gun, while the coils, wrought-iron, and 
initial tension, make it essentially an Armstrong gun. It is a Fraser 
gun, too, with a thick outer coil, where a thick coil ought, and ought 
only, to be. The only novelty I claim is the new principle whereby it 
is possible to reconcile all these great authorities.* 
Breech-Loading . 
In addition to the advantage of great strength, breech-loading comes 
in as a most important element in the gain which will be obtained by 
this method of construction. 
■* No doubt these advantages might be combined in any breech-loader which had a wrought-iron 
barrel and steel breech-piece, but not so effectually as in this gun. I may, however, claim the 
combination independently of my system of breech-loading. 
