THE ROYAL ARTILLERY INSTITUTION. 
65 
plates of iron would be indubitably pierced by these projectiles, even at 
great distances. 
“The gun (A) burst at the 66th round. 
6. “ After a very close investigation into all possible causes of this 
explosion, and after a careful examination of the fragments, as well as of 
those of the shots fired, the cause of the accident has been decided to be, 
(1) “ That the projectile was not centred in the bore, 
(2) “ That the zinc studs were not strong enough, and were sheered by the 
movement of the projectile in the bore. 
“ Under these circumstances the body of the projectile must have rubbed 
the sides and produced bulges which increased with every round, and had 
the effect of at last wedging it in the bore. It was inevitable that the gun 
must then burst if the charge were strong enough.* 
7. “The second trial took place with a rifled cannon of 8*58 inches (JB). 
As for the*reason which led to the step from a cannon of 9’65 inches to that 
of 8*58 inches, it is this : The 9 # 65 inch gun firing a projectile of £70 lbs. 
was too light in itself; the weight of the piece was only equivalent to 61 
projectiles, and it acted in consequence in a destructive manner on the 
carriage. To avoid this inconvenience it would have been necessary either 
to augment the weight of the gun or to give up the use of projectiles of 
£70 lbs., changing the construction of the latter for some other less 
advantageous and much lighter form. 
“The difficulties which have been experienced in the course of the 
introduction of heavier cannon, whether of solid structure or strengthened 
with iron or steel cylinders, and the necessity which was acknowledged of 
selecting as favourable a form of projectile as possible, while at the same time 
the piece should weigh about 100 times the weight of the shot, led to the 
determination to adopt a calibre of 8*58 inches, instead of 9*65 inches, and 
to bore the 9*65 inch block accordingly. 
“Trial was therefore made of an 8* 5 8-inch gun rifled with parallel grooves, 
constructed on the foregoing principles, and firing projectiles of ££0 lbs., 
with a charge of 33 lbs. pellet powder (A). 
8. “ In the preparation for this experiment all possible care was taken to 
prevent the wedging of the shot in the bore of the gun. The studs were for 
greater strength made of copper, and their number increased: besides the 
driving studs, two rows of centering studs were applied, which bore on the 
lands, and were intended to prevent the contact of the projectile with the 
cylinder in issuing from the gun. With the same intention the cylindrical 
body of the projectile was so proportioned that under no circumstances 
could it touch the bore, with whatever manufacturing error the parts above 
described might be affected; the surface of the projectiles was turned, and a 
* The official reader is referred to the Journal of the Commission 2, 3, December, 1863, for 
further particulars. 
