1), which rises at the opposite end and allows catch B to fly
forward and release the piece of broom-stick C. The weight D then
falls and jerks up the hook-lock M, which unlocks the door, and
the heavier weight N immediately opens it.
Thus, with a switch as in Fig. 3, the door can only be opened by
the person who has the key, for the circuit cannot be closed with
an ordinary nail or wire. B, Fig. 2, shows catch B, Fig. 1,
enlarged; 0, Fig. 2, is the cut through which the rope runs; H,
Fig. 1, is an elastic that snaps the catch back into place, and at
G the wires run outside to the keyhole.
This arrangement is very convenient when one is carrying something
in one hand and can only use the other. Closing the door winds up
the apparatus again.
--Contributed by E. H. Klipstein, 116 Prospect St., East Orange,
New Jersey.
** Parlor Magic for Winter Evenings [90]
By C. H. CLAUDY
You are seated in a parlor at night, with the lights turned low.
In front of you, between the parlor and the room back of it, is an
upright square of brightly burning lights, surrounding a perfectly
black space.
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