cked it to the boards. This
not only keeps the rats out, but prevents the chickens from
digging holes, thus helping the rats to enter.
--Contributed by John A. Hellwig, Albany, N. Y.

** Homemade Telephone Receiver [353]

The receiver illustrated herewith is to be used in connection with
the transmitter described elsewhere in this volume. The body of
the receiver, A, is made of a large wooden ribbon spool. One end
is removed entirely, the other sawed in two on the line C and a
flange, F, is cut on the wood, 1/8 in. wide and 1/16 in. deep. A
flange the same size is made on the end D that was sawed off, and
the outside part tapered toward the hole as shown. The magnet is
made of a 30-penny nail, B, cut to the length of the spool, and a
coil of wire, E, wound on the head end. The coil is 1 in. long,
made up of four layers of No. 22 gauge copper magnet wire,
allowing the ends to extend out about 6 in. The nail with the coil
is then put into the hole of the spool as shown. The diaphragm C,
which is the essential part of the instrument, should be made as
carefully as possible from ferrotype tin, commonly called tintype
tin. The diaphragm is placed between the flanges on the spool and
the end D that was sawed off. The end piece and diaphragm are both
fastened to the spool with two or three slender wood screws, as
shown.

A small wooden or fiber end, G, is fitted with two binding posts
which are connected to the ends of the wire left projecting from
the magnet winding. The binding posts are attached to the line and
a trial given. The proper distance must be found between the
diaphragm and the head of the nail. This can be accomplished by
moving

[Illustration: Receiver]

the nail and magnet in the hole of the spool. When the distance to
produce the right sound is found, the nail and magnet can be made
fast by filling the open space with melted sealing wax. The end G
is now fastened to the end of the spool, and the receiver is ready
for use.

** How to Clean Jewelry [353]

To cleanse articles of silver, gold, bronze and brass use a
saturated solution of cyanide of potassium. To clean small
articles, dip each one into the solution and rinse immediately in
hot water; then dry and polish with a linen cloth. Larger articles
are cleaned by rubbing the surface with a small tuft of cotton
saturated in the solution. As cyanide of potassium is a deadly
poison, care must be taken not to have it touch any sore spot on