tions. The rate of flow is often very
slow; sometimes only one or two feet a day, but, no matter how
slow the motion may be, the large body of ice has to bend in
moving.

This property of ice is hard to illustrate with the substance
itself, but may be clearly shown by sealing-wax, which resembles
ice in this respect. Any attempt to bend a piece of cold
sealing-wax with the hands results in breaking it, but by placing
it between books, as shown on page 65, or supporting it in some
similar way, it will gradually change from the original shape A,
and assume the shape shown at B.

** Return-Call Bell With One Wire [101]

[Illustration: Wiring Diagram]

To use only one wire for a return call bell connect up as shown in
the diagram, using a closed circuit or gravity battery, B. The
current is flowing through both bells all the time, the same as
the coils of a telegraph sounder, but is not strong enough to ring
both connected in series. Pressing either push button, P, makes a
short circuit of that bell and rings the one at the other end of
the line.
--Contributed by Gordon T. Lane, Crafton, Pa.

** Circuit Breaker for Induction Coils [101]

Amateurs building induction coils are generally bothered by the
vibrator contacts blackening, thus giving a high resistance
contact, whenever there is any connection made at all. This
trouble may be done away with by departing from the old
single-contact vibrator and using one with self-cleaning contacts
as shown. An old bell magnet is rewound full of No. 26 double
cotton-covered wire and is mounted

[Illustration: Interrupter for Induction Coil]

upon one end of a piece of thin sheet iron 1 in. by 5 in. as per
sketch. To the other end of the strip of iron is soldered a piece
of brass 1/64 in. by 1/4, in. by 2 in., on each end of which has
been soldered a patch of platinum foil 1/4 in. square.

The whole is connected up and mounted on a baseboard as per
sketch, the contact posts being of 1/4 in. by 1/2 in. brass, bent
into shape and provided with platinum tipped thumb screws. The
advantage of this style of an interrupter is that at each stroke
there is a wiping effect at the heavy current contact which
automatically cleans off any carbon deposit.

In the wiring diagram, A is the circuit breaker; B, the induction
coil, and C, the battery.
--Contributed by A. G. Ward, Wilkinsburg, Pa.

** Spit Turned by Water Power [102]

Many of the Bulgarian peasants do their