of fine wire, such

[Illustration: Medical Induction Coil]

as used on telephone generators, around the coil, leaving long
terminals. Soak the whole in melted paraffin and let cool; bind
tightly with black silk.

The vibrator is made of a piece of thin tin to which is soldered
the head of an iron screw and on the other side a small piece of
platinum, which can be taken from an old electric bell (Fig. 2).

Of course, a regulator must be had for the vibrator; this can be
accomplished by bending a stout piece of copper wire as shown. The
connections and the base for setting up are shown in the figures.
--Contributed by J. T. R., Washington, D. C.

** Mechanical Trick With Cards [63]

The following mechanical card trick is easy to prepare and simple
to perform:

First, procure a new deck, and divide it into two piles, one
containing the red cards and the other the black ones, all cards
facing the same way. Take the red cards, square them up and place
in a vise. Then, with a plane, plane off the upper right hand
corner and lower left hand corner, as in Fig. 1, about 1/16 in.

Then take the black cards, square them up, and plane off about
1/16 in. on the upper left hand corner and lower right hand
corner, as in Fig. 2.

Next restore all the cards to one pack, taking care to have the
first card red, the next black, and so on, every alternate card
being the same color. Bend the pack so as to give some spring to
the cards, and by holding one thumb on the upper left-hand corner

[Illustration: Card Trick]

all the cards will appear red to the audience; place thumb in the
center at top of pack and they will appear mixed, red and black;
with thumb on upper right-hand corner all cards appear black. You
can display either color called for.
--Contributed by Ralph Gingrich, Chicago.

** How to Make a Rain Gauge [64]

An accurate rain gauge may be easily constructed from galvanized
iron, as shown in the sketch herewith. The funnel, A, overlaps and
rests on the body, B, and discharges into the tube, C, the area of
which is one-tenth that of the top of the funnel. The depth of the
water in C is thus ten times the actual rainfall, so that by
measuring it with a stick marked off in tenths of an inch, we
obtain the result in hundredths of an inch.

A good size to make the rain gauge is as follows: A, 8 in.
diameter; C, 2.53 in. ; length of C, about 20 in. It should be
placed in an exposed location, so that no ina