the valve. The air passes up through the center of the base, the pipe
connecting with one of the hollow trunnions. The valve is a continuation
of the breech of the gun. The smaller cuts illustrate Lieutenant
Zalinski's plan for mounting the gun on each side of the launch, by
which plan the gun after being charged may have the breech containing
the dynamite depressed, and protected from shots of the enemy by its
complete immersion alongside the launch; and, if necessary, may be
discharged from this protected position. The gun is a seamless brass
tube of about forty feet in length, manipulated by the artillerist in
the manner of an ordinary cannon. Its noiseless discharge sends the
missile with great force, conveying the powerful explosive within it,
which is itself discharged internally upon contact with the deck of a
vessel or other object upon which it strikes, through the explosion of a
percussion fuse in the point of the projectile. A great degree of
accuracy has been obtained by the peculiar form of the projectile.

[Illustration: PNEUMATIC DYNAMITE GUN TORPEDO VESSEL.]

The projectile consists of a thin metal tube, into which the charge is
inserted, and a wooden sabot which closes it at the rear and flares out
until its diameter equals that of the bore of the gun. The forward end
of the tube is pointed with some soft material, in which is embedded the
firing pin, a conical cap closing the end. A cushion of air is
interposed at the rear end of the dynamite charge, to lessen the shock
of the discharge and prevent explosion, until the impact of the
projectile forces the firing pin in upon the dynamite and explodes it.
Many charges have been successfully fired at Fort Hamilton, N.Y. As the
center of gravity is forward of the center of figure in the projectile,
a side wind acting upon the lighter rear part would tend to turn the
head into the wind and thus keep it in the line of its trajectory. A