ctric current can undo the work of a strong one.

I once tried to electrocute a rat which was caught in a wire
basket trap and accidentally discovered a painless method. I say
painless, because the rodent does not object to a second or third
experiment after recovering, and is apparently rigid and without
feeling while under its influence.

To those who would like to try the experiment I will say that my
outfit consisted of an induction coil with a 3/8-in. iron core
about 3 in. long. The primary coil was wound with four layers of
No. 20 wire and the secondary contains 4 oz. No. 32 wire, and used
on one cell of bichromate of potash plunge battery. The proper
amount of current used can be determined by giving the rodent as
much as a healthy man would care to take. Fasten one secondary
electrode to the trap containing the rat and with a wire nail
fastened to the other terminal, hold the vibrator of the coil with
your finger and let the rat bite on the nail and while doing so
release the vibrator. In three seconds the rat will be as rigid as
if dead and the wires can be removed.

Now connect your wires to the primary binding-posts of the coil
and wind the end of one of them around the rat's tail and start
the vibrator. Touch the other terminal to the rat's ear and nose.
In a few minutes he will be as lively as ever.
--Contributed by Chas. Haeusser, Albany, N. Y.

** A Simple Battery Rheostat [445]

A spring from an old shade roller is mounted on a board 4 in.
wide, 9 in. long and 3/8 in. thick. A binding-post is fastened to
this board at each end, to which is attached the ends of the
spring, as shown in Fig. 1. The temper of a small portion of each
end of the

[Illustration: Battery Rheostat]

spring will need to be drawn. This can be accomplished by heating
over an alcohol lamp or in a fire and allowing it to cool slowly.
The ends are then shaped to fit the binding-posts. A wire is
connected to one of the binding-posts and a small square piece of
copper is attached to the other end of the wire, as shown in Fig.
2. When this device is placed in a circuit the current can be
regulated by sliding the small square copper piece along the
spring.
--Contributed by H. D. Harkins, St. Louis, Mo.

** A Frame for Drying Films [446]

[Illustration: Frame]

No doubt many amateur photographers are troubled about drying
films and to keep them from curling. The problem may be solved in
the following way:

Make a r