1872.] Notices of Books. 365 
through its rough process of manufacture, many details neces- 
sarily being omitted. First, the gun consists of the following 
parts :-— 
I. An inner barrel or tube of steel, called the A tube. 
II. Two single and slightly taper coils united together, called 
the B Tube. 
III. A triple coil, a trunnion ring, and a double coil, all welded 
together, called the breech-coil or jacket. 
IV. A cascable. 
I. The steel for the A tube is received from the contractors in 
the form of a solid ingot and severely tested. It is next roughly 
bored and turned and becomes a tube, which is next toughened 
by being thoroughly heated to a certain temperature, and then 
plunged in a bath of oil until cool. This process frequently 
warps the steel tube, and not unfrequently causes the surface to 
crack ; the barrel is therefore slightly turned and bored again to 
make it straight inside and out, as well as to remove any slight 
flaws; and for fear some of these flaws should escape notice, 
the tube is now subjected to the water-test. By certain 
mechanical contrivances the tube is filled with water, which 
is subjected to a pressure of 34} tons per square inch; if no mois- 
ture exudes on the exterior of the barrel under this pressure the 
tube is passed as sound. 
II. The B tube is composed of two coils made and welded 
together in the usual way, and rough- and fine-bored to the degree 
of smoothness requisite for close contact with the steel A tube 
on which it is to be shrunk; and here it may be remarked, that it 
is found easier to turn an inner tube to fit an outer one than vice 
versa. 
III. The triple coil is formed by coiling three bars one over the 
other and welded under a powerful steam-hammer and turned 
down, being fitted with a shoulder for the reception of the 
trunnion ring. 
The double coil is similarly prepared also to fit the trunnion 
ring, the trunnion ring being also ready; all three parts are 
heated to redness, the trunnion ring is dropped upon the shoulder 
of the triple coil, and the double coil dropped through the 
upper part of the trunnion ring on the triple coil, and the whole 
mass placed bodily in a furnace and raised to welding heat ; 
being next placed under the most powerful hammer in the 
department, six or seven blows suffice to amalgamate the three 
parts together. The breech coil thus formed is next turned in a 
very powerful lathe, the trunnion ring slotted smooth in a self- 
acting vertical machine, and the trunnions themselves turned 
down to shape in a break lathe. The jacket is next rough- and 
fine-bored, and its muzzle end recessed on the inside so as to 
overlap the breech end of the B tube. 
