s, copper, German silver,
nickel and such metals, silver can be plated direct. The deposit
of silver will be dull and must be polished. The best method is to
use a revolving scratch brush; if one does not possess a buffing
machine, a hand scratch brush is good. Take quick, light strokes.
Polish the articles finally with ordinary plate powder.

The sketch shows how to suspend the articles in the plating-bath.
If accumulators are used, which is advised, be sure to connect the
positive (or red) terminal to the piece of silver hanging in the
bath, and the negative (or black) terminal to the article to be
plated. Where Bunsen cells are used, the carbon terminal takes the
place of the positive terminal of the accumulator. --Model
Engineer.

** An Ingenious Electric Lock for a Sliding Door [89]

The apparatus shown in Fig. 1 not only unlocks, but opens the
door, also, by simply pressing the key in the keyhole.

In rigging it to a sliding door, the materials required are: Three
flat pulleys, an old electric bell or buzzer, about 25 ft. of
clothesline rope and some No. 18 wire. The wooden catch, A (Fig.
1), must be about 1 in. thick

[Illustration: Electric Lock for Sliding Door]

and 8 in. long; B should be of the same wood, 10 in. long, with
the pivot 2 in. from the lower end. The wooden block C, which is
held by catch B, Can be made of a 2-in. piece of broomstick. Drill
a hole through the center of this block for the rope to pass
through, and fasten it to the rope with a little tire tape.

When all this is set up, as shown in Fig. 1, make a key and
keyhole. A 1/4 in. bolt or a large nail sharpened to a point, as
at F, Fig. 3, will serve for the key. To provide the keyhole, saw
a piece of wood, I, 1 in. thick by 3 in. square, and bore a hole
to fit the key in the center. Make a somewhat larger block (E,
Fig. 3) of thin wood with a 1/8-in. hole in its center. On one
side of this block tack a piece of tin (K, Fig. 3) directly over
the hole. Screw the two blocks together, being careful to bring
the holes opposite each other. Then, when the point of the key
touches the tin, and the larger part (F, Fig. 3) strikes the bent
wire L, a circuit is completed; the buzzer knocks catch A (Fig.
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.