A similar experiment
consists in first turning on the red light for about a minute and
then turning it off at the same time that the white one is turned
on. The entire screen will then appear to be a vivid green for
about one second, after which it assumes its normal color.
** To Explode Powder with Electricity [53]
A 1-in. hole was bored in the center of a 2-in. square block. Two
finishing nails were driven in, as shown in the sketch. These were
connected to terminals of an induction coil. After everything was
ready the powder was poured in the hole and a board weighted with
rocks placed over the block. When the button is pressed
[Illustration: Exploding Powder]
or the circuit closed in some other way the discharge occurs. The
distance between the nail points--which must be bright and
clean--should be just enough to give a good, fat spark.
--Contributed by Geo. W. Fry, San Jose, Cal.
** Simple Wireless System [54]
The illustrations will make plain a simple and inexpensive
apparatus for
[Illustration: Simple Wireless System]
wireless telegraphy by which I have had no difficulty in sending
messages across 1-1/2 miles of water surface.
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