space filled with air, a space filled with powder giving off gas, which
comes into play as the projectile travels down the bore. Thus, while not
exceeding the intended pressure at the breech, the pressure toward the
muzzle is kept up, and the velocity very materially increased. Following
this principle to this conclusion, it will be found that the perfect
charge for a gun will be one which exactly fills the chamber, and which
is composed of a powder rather too slow to give the pressure for which
the gun is designed, supposing the shot to move off freely. The powder
should be so much too slow as to require for its full development the
holding power of a band which is just strong enough to give rotation to
the shot.

Having settled that the gun of the future is to be a breech-loader,
we have next to consider what system of closing the breech is to be
adopted.

The German guns are provided with a round backed wedge, which is pushed
in from the side of the breech, and forced firmly home by a screw
provided with handles; the face of the wedge is fitted with an easily
removable flat plate, which abuts against a Broad well ring, let into
a recess in the end of the bore. On firing, the gas presses the ring
firmly against the flat plate, and renders escape impossible as long as
the surfaces remain uninjured. When they become worn, the ring and
plate can be exchanged in a few minutes. Mr. Vavasseur, of Southwark,
constructs his guns on a very similar plan. In the French guns, and our
modern ones, the bore is continued to the rear extremity of the piece,
the breech end forming an intermittent screw, that is, a screw having
the threads intermittently left and slotted away. The breech block has
a similarly cut screw on it, so that when the slots in the block
correspond with the untouched threads in the gun, the block can be