THE EIGHTY-TON GUN, OR WOOLWICH INFANT. 
247 
to the trucks. The direct strain the carriage must, under any 
circumstances, bear ; but this is not what it generally suffers from, 
but rather the contortion that it receives, from the fact that the 
centre of gravity of the mass cannot be brought opposite to the 
bottom of the bore of the gun, but must fall below it. A 
violent horizontal blow backwards, opposed by a resistance in a 
lower plane, causes obviously a contorting “ couple” or twist to be 
generated, driving the posterior part of the carriage against the 
ground, and, as a secondary effect, causing the front of it to lift 
or jump. In our modern heavy gun-carriages this has been 
brought to a minimum by getting the gun well down between 
the brackets or cheeks of the carriage, and making the latter as 
low as possible, so that the bottom of the bore, the centre of 
gravity of the mass, and the surface on which the carriage 
slides as it recoils, are brought as nearly into the same plane 
as possible. With the 80-ton carriage (vide PI. CXXXVII. 
fig. 2) the evil could not be got over in this way; for the 
gun-carriage trucks, which were to be also railway trucks, 
must be capable of running along rails, and round any curves 
that might exist. The carriage was necessarily very long, 
the length of the gun itself being 27 feet. Consequently, 
the only way in which it could be made to turn, was to 
construct it in the form of an upper carriage resting on 
“ bogies” (vide fig. 2). Each of these bogies being attached to 
the carriage by a single centre pivot, the whole might run 
round any curve that the bogies could take independently, the 
carriage adjusting itself like a flexible connection. This, how- 
ever, necessitated the gun being a considerable height above the 
trucks, and so called for great strength in the carriage, which 
would be severely taxed by a downward contorting blow on 
firing. The carriage is made of iron, except a wood block 
termed a buttress, which supports the trunnion-hole block at 
a, and a few other minor parts. Strong india-rubber springs, 
or buffers of sheet india-rubber an inch thick, are laid in between 
pieces of iron plate at c c, above the trucks, to prevent shocks 
or jars in travelling. Hand-wheels are fixed on the front and 
rear of the ends of the front and rear bogies respectively, which, 
by means of bell-crank gear, bring double wood brakes to bear on 
all the trucks. The platform of each bogie consists of longitu- 
dinal pieces of angle iron, 12 inches by 6 inches, with 1-J-inch 
web. The carriage rests on gun-metal bearings on the bogies. 
From what has been said it may be seen that, on firing, a 
violent backward and downward blow will be given to the carriage 
through the trunnion blocks at e and F. Here again is india- 
rubber inserted under pressure, to act as a cushion. It may be 
seriously doubted how this would do in hot climates. For the 
service for which the carriage is at present intended, however, it 
