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.
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