wide, and 1/8 in. thick. The connection between two adjoining
strips is made by a copper cartridge, C, which is dropped in a hole in
the frame bored to receive it. This cartridge is the one used in the
Springfield rifle. Inside the cartridge is a spiral spring, S, which,
acting on the bottom of the hole and the head of the cartridge, tends
to make the latter spring up, and so break the circuit.
To the hook, H, which is attached to the cartridge, is suspended, by
means of a string, the lead weight, W, thus drawing down the cartridge
and making the circuit between A and A'. All the weights being
suspended the current comes in through the post, P, passes along the
copper strips and out of the corresponding post on the other end.
On firing the projectile cuts a string, and the spring at once causes
the cartridge to spring up, thus breaking the circuit.
It is not possible for the projectile to squeeze between the strings
and not break the current, for in so doing the cartridge is tipped
slightly, which is sufficient, as it breaks the current on one side.
This target is used in connection with the Boulenge chronograph. Two
targets are established at a known distance apart, say 50 ft.
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