by a flexible wire cord to
the knob B. The cord is also fastened to a lever, C, which is
pivoted at D and is released by a magnetic trigger, E, made from
the armature and magnet of an old electric bell.

When the circuit is completed by means of a secret contact device
outside the door, the magnet, F, pulls down the armature, which
releases the trigger and allows the spring to open the lock. If
there are metal numbers on the outside of the door they may be
used for the secret contact, if desired,

[Illustration: Apparatus Placed on Inside of Door]

but if there are no numbers on the door, a small contact-board may
be constructed by driving about 12 brass headed tacks into a thin
piece of wood and making connections at the back as shown in the
wiring diagram.

In this particular diagram the tacks numbered 1 and 7 are used for
unlocking the door, the others being connected with the
electric-bell circuit as indicated, for the purpose of giving an
alarm should anybody try to experiment with the secret contacts.
By means of a pocket knife or other metal article the operator can
let himself in at any time by connecting the tacks numbered 1 and
7, while a person not knowing the combination would be liable to
sound the alarm. Of course, the builder of this device may choose
a combination of his own and may thus prevent anybody else from
entering the door, even those who read this description.
--Contributed by Perry A. Borden, Gachville, N. B.

[Illustration: Wiring Diagram]

** How to Tighten a Curtain-Roller Spring [79]

A common table fork can be used to hold the little projection on
the end of a curtain roller for tightening the spring. Hold the
fork firmly with one hand while turning the roller with the other.
Do not let go of the fork until the little catches are set in
position to prevent the spring from turning, or else the fork may
be thrown off with dangerous force.

** Alarm Clock Chicken Feeder [79]

An automatic poultry feeder, which will discharge the necessary
amount of corn or other feed at any desired time, may be made by
using an alarm clock as shown in the sketch. A small wire trigger
rests on the winding key and supports the swinging bottom of the
food hopper by means of a piece of string which connects the two.
When the alarm goes off the trigger drops and allows the door to
open, thus discharging the contents of the hopper.

After the device has been in operation for some time the hens