courses. When the connecting rings are fitted on, the barrel not being
fired will remain practically straight, and, as it is coupled to the
barrel being fired by the rings, the muzzle of the latter will be
restrained from pointing outward.

The result will be as shown in an exaggerated manner by the dotted
lines on the right barrel in Fig. 3.

It would appear from these experiments that when very accurate
shooting is required at long ranges with double-barreled rifles, they
should be mounted in a manner similar to that adopted in the
manufacture of the Nordenfelt machine gun, in which weapon the barrels
are fitted into a plate at the extreme breech end, the muzzles
projecting through holes bored to receive them in a metal plate. No
unequal expansion would then take place, and the barrels would be free
to become shorter independently of each other. We give the above
experiments on the authority of their author, who, we believe, has
taken great pains to render them as exhaustive as possible, so far as
they go.--_Engineering._

* * * * *




BALL TURNING MACHINE.


The distinguishing feature in the ball turning machine shown opposite
is that the tool is stationary, while the work revolves in two