64 
POPULAR SCIENCE REVIEW. 
a hostile ram to give her a fair blow, but should she receive 
injury her peculiar structure — by which she is divided into an 
under and upper portion, with numerous water-tight compart- 
ments — would keep her afloat even with a large breach in her 
side. In addition to the ordinary bulkheads running across the 
ship, she will have one dividing her amidships in the direction 
of her length, and separate bulkheads specially constructed to 
isolate and protect the engines and boilers. In all, she will 
contain no less than 127 water-tight compartments; but 
numerous as they are, care has been taken to plan them so as 
not to interfere with the working of the vessel. The bottom 
will be double, and divided into several cells, in order to pre- 
vent any extensive injury from the explosion of a torpedo. 
The armament of the Inflexible will be composed of four of 
the heaviest guns ever constructed, of which the experimental 
81 -ton gun now being tested at Woolwich is the type. Fig. 2 
is a sectional sketch of the gun, showing the arrangement of 
the wrought-iron coils welded round the massive central steel 
tube. This tube, which forms the core of the gun, is bored out 
of a solid ingot, which cost about 1,700£. The bore is 24 ft. 
long, and rifled from the muzzle to within a few feet of the base 
of the tube, where the unrifled portion forms the powder 
chamber. The greatest external diameter of the gun is 6 ft. ; at 
the muzzle it is just 2 ft. in diameter. The full calibre of the 
piece will be 16 in. The experimental gun has as yet been only 
bored out to 14^ in. ; for the second series of experiments it 
will be given a calibre of 15 in. ; it will then be bored to the 
full calibre of 16 in. and finally tested. Meanwhile the four 
guns which are actually to be mounted in the turrets of the 
Inflexible are in process of manufacture at Woolwich Arsenal. 
The following are the approximate weights of the charges and 
projectiles for the various calibres of the 81 -ton gun : — 
Calibre. 
Charge. 
Projectile. 
inches. 
lbs. 
lbs. 
14 * 
220 
1,250 
15 
250 
1,350 
16 
300 
1,650 
The 16-in. shell of the 81 -ton gun will weigh nearly three- 
quarters of a ton ; the bursting charge will be about a hundred 
pounds, that is, a whole barrel of gunpowder. Only the first 
series of experiments (those with the calibre of 14^ in.) is com- 
plete, and the gun is now being bored out to 15 in. The expe- 
riments occupied four days — Sept. 16, Nov. 18, and Dec. 9th and 
10th, and gave excellent results. The coils and the steel tube 
bore the enormous strain without receiving the least injury or 
displacement, while the gun gave a very high initial velocity to 
