410 
MINUTES OF PROt .EDINGS OF 
the first round of proof, and many were startled by the occurrence, as it 
was commonly believed that a coiled wrought-iron gun would not burst 
explosively, but better informed people knew well that instances had already 
occurred of their doing so—for instance, the 9*22 inch of original construction 
before alluded to, burst in this manner with a service charge, and two 40-pr. 
B.L. guns actually went to atoms whilst proving vent-pieces; these guns 
were no doubt old and worn out, and had given timely indications of their 
dangerous condition, but it was also known that new guns would go in the 
same manner, if their elasticity or strength were subjected to a too sudden 
or a too excessive strain, such as that exerted by the action of some violent 
explosive like gun-cotton or nitro-glycerine, or from an intolerably large 
charge of powder. Now, the bursting of the 9-inch gun at proof, was 
evidently due to a defective tube, for one of the ills which a steel barrel is 
heir to are cracks, imperceptible and often very deep, caused probably by 
the unequal rate of cooling of some of the parts during the process of 
toughening. A gun with a tube so diseased may well be compared to 
“ a goodly apple rotten at the coresuch was the gun in question, and it 
was no w r onder that the powerful proof charge (53J lbs.) should have blown 
it to pieces at the first round. 
To prevent, however, a similar occurrence, every steel tube is now subjected 
after toughening to a water pressure on the interior of 8000 lbs. per square 
inch, which is sufficient it is thought to detect any latent cracks. Any gun 
that has stood the proof may safely be relied on as free from these dangerous 
defects. 
Final Trial of 9-inch, Guns . 
In order, however, to set the matter at rest, further trials with “ Eraser 99 
9-inch guns were recommended and approved, the results of the former 
experiments being deemed inconclusive, as the vents of the guns happened 
to be at the rear—which fact causes a less strain on the piece than when 
it is some distance forward, as in the service guns. Expl. No. 332 gun, 
which had already fired 400 rounds with full charges (30 lbs.) and 214 
with battering charges (43 lbs.) with the rear vent, was accordingly turned 
upside down and vented in the service position, and subjected to a crucial 
test of 500 rounds with battering charges at 50 rounds a-day, which it 
finished most triumphantly, 11th March, 1869; so that this gun fired 
altogether 1114 rounds, of which 714 were with battering charges—a great 
increase on the number of rounds to which the service of 9-inch guns was 
limited in 1866 ! 
A new 9-inch gun, Expl. No. 368, of the service pattern—that is, reinforced 
with a triple coil like the gun that burst—was then subjected to the same 
test as No. 332 had undergone, in order to ascertain which of the two 
modifications of the new construction was the stronger. It fired 400 rounds 
with full, and 207 with battering charges, with the vent in rear; it w r asthen 
turned over, vented in the service position, and the second part of the 
programme, namely 500 rounds with battering charges, was commenced. 
At the 100th round the impressions showed a faint crack in the steel tube 
at the crown of the bore. This increased regularly to the 401st round— 
that is, the 1008th round of all—when the gas escape indicated that the 
