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Last year Mr. Whitworth, taught by his previous failure, and rightly 
attributing the success of the Armstrong gun to ts strength, himself . 
adopted the same principle of construction for his 80-pounder gun. This 
he made of a tube of what he calls homogeneous iron, and tapering 
slightly outside. On this conical tube he forced short tubes of wrought- 
iron, and over these a third layer of tubes. This method of putting 
tubes together is, I think, much better than that used by the French 
Government and by Sir William Armstrong, who heat the outer tubes and 
allow them to shrink on the inner ones. 
Within the last few months Sir W. Armstrong has attempted an 
imitation of my 1855 gun for our navy. His new naval guns are 64 
inches in bore. The interior is of cast-iron, about 6 inches thick from 
the breech to just behind the terminus, where the thickness is suddenly 
increased to 84 inches. I need hardly say they must break at this 
point. The weight is 98 cwt., and they cannot be depended on to fire 
the 70 lb. shells for which they were constructed. I mention them to 
point out the real cause of failure, which has been wrongly attributed to 
the circumferential strength obtaimed by the double layer of metal at 
the breech being sufficient. To rebut this, [ need only say that a 10-inch 
gun built up of only two layers, but of better proportions, stood 10 
rounds with 20 lbs. powder and 132-pound shot; 10 rounds with 20 lbs. 
powder and 264 lb. bolt; 10 rounds with 20 Ibs. powder and 396-pound 
bolt ; 9 rounds with 20 lbs. powder and 512-pound bolt. 
That gun, though LIGHTER THAN THE NEW NAVAL GUN BY HALF A TON, 
would never have burst with 70 lb. shells! 
I last year made a gun something like this in form, and only half 
the weight of the new naval gun, 48 cwt. instead of 98. From it I 
have thrown 58 lb. shells with a greater velocity than such shells have 
ever before been thrown. One of my objects in making this gun was 
to prove that the efficiency of a rifled cannon depended principally on 
its strength—strength which has yet been obtained in one way only— 
for cannon of any size, viz., by building them up in at /east two layers. 
I fired Mr. Bashley Britten’s shells, already described, and obtained 
sach great velocity that they flew above a mile and a half (2670 yards) 
with only 5° elevation. It is but a short time since Sir W. Armstrong 
thought it much to do this with double the elevation. The range of 
Mr. Whitworth’s 80-pounder, solid shot, with 5° elevation, is reported 
to have been less than that of the 58 lb. hollow shells I fired, but, as the 
wind may have favoured me, I have invited him to a friendly trial of 
our respective guns at the same time and place. 
I have now endeavoured to show that no rifled cannon of consider- 
able size have succeeded when made in one mass; that all French, 
Sardinian, Armstrong, Whitworth, and my own, have succeeded when 
built up, all except the new naval gun, which fails from obvious causes; 
and, lastly, that the success of successful rifled cannon has been due 
neither to their having thirty-six grooves, nor to their being polygonal 
in section, but to their strength. 
