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
range of 11/4 miles has been attained with the two inch gun, with a
pressure of 420 lb. to the square inch, and one of three miles is hoped
for with the larger gun and a pressure of 2,000 lb.

* * * * *

ROPE PULLEY FRICTION BRAKE.

A novel device in connection with rope pulley blocks is illustrated in
the annexed engravings, the object of the appliance being to render it
possible to leave a weight suspended from a block without making the
tail of the rope fast to some neighboring object. By this arrangement
the danger of the rope slipping loose is avoided, and absolute security
is attained, without the necessity of lowering the weight to the ground.
The device itself is a friction brake, constructed in the form of a clip
with holes in it for the three ropes to pass through. It is made to span
the block, and is secured partly by the pin or bolt upon which the
sheaves run, and partly by the bottom bolt, which unites the cheeks of
the block. Thus the brake is readily attachable to existing blocks. The
inner half of the clip or brake is fixed solidly to the block, while the
outer half is carried by two screws, geared together by spur-wheels, and
so cut that although rotating in opposite directions, their movements
are equal and similar. One of the screws carries a light rope-wheel, by
which it can be rotated, the motion being communicated to the second
screw by the toothed wheels. When the wheel is rotated in the right
direction the loose half of the clip is forced toward the other half,
and grips the ropes passing between the two so powerfully that any
weight the blocks are capable of lifting is instantly made secure, and
is held until th