** Another Electric Lock [110]
The details of the construction of an electrically operated lock
are shown in the illustration. When the door is closed and the
bolt A pushed into position,
[Illustration: Simple Electric Lock]
it automatically locks. To unlock, push the button D, which act
will cause the electromagnet to raise the latch C, when the bolt
may be drawn and the door opened.
--Contributed by A. D. Zimmerman, Boody, Ill.
** How to Mix Plaster of Paris [110]
For the mixing of plaster of Paris for any purpose, add the
plaster gradually to the water, instead of the contrary, says the
Master Painter. Do not stir it, just sprinkle it in until you have
a creamy mass without lumps. Equal parts of plaster and water is
approximately the correct proportion. The addition of a little
vinegar or glue water will retard the setting of the plaster, but
will not preserve its hardening. Marshmallow powder also retards
the setting. In this way the plaster may be handled a long time
without getting hard. If you wish the plaster to set extra hard,
then add a little sulphate of potash, or powdered alum.
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