h [121]
By ARTHUR E. JOERIN

An efficient wireless-telegraph receiving apparatus for distances
up to 1,000 ft. may be constructed in the following manner: Attach
a watchcase telephone receiver to a dry cell, or battery, of any
make. The negative pole, or zinc, of the cell is connected to a
ground wire. This is done by attaching to a gas or water pipe. The
positive pole, or carbon, of the cell is connected to the aerial
line. This aerial collector can be made in various ways, either by
using a screen wire or numerous wires

[Illustration: For Distances up to 1000 Feet]

made in an open coil and hung in the air. File a V-shaped groove
in the upper end of the carbon of the cell. Attach a small bent
copper wire in the binding post that is attached to the zinc of
the cell. In the bend of this wire and the V-shaped groove filed
into the carbon, lay a needle. This will complete the receiving
station. Use a spark coil in connection with a telegraph key for
the sending station, making a ground with one wire, and have the
other connected with another aerial line.

By connecting the telephone receiver to the cell and at the same
time having a short circuit a receiving station is made. As the
telephone offers a high resistance, part of the current will try
to take the shorter high resistance through the needle. If the
waves strike across the needle, the resistance is less, and thus
less current travels through the telephone receiver. If the wave
ceases, the resistance between the needle and the carbon is
increased, and as less current will flow the short way, it is
compelled to take the longer metallic way through the windings of
the receiver, which will cause the clickings that can be heard.

** To Preserve Putty [121]

Putty, when left exposed to the air, will soon become dry and
useless. I have kept putty in good condition for more than a year
by placing it in a glass jar and keeping it entirely covered with
water.

** How to Make a Small Storage Battery [121]

The cell of a storage battery consists of two plates, a positive
and a negative, made of lead and placed in a dilute solution of
sulphuric acid. Large batteries made of large cells have a great
number of plates, both positive and negative, of which all
positive plates are connected to one terminal and the negative
plates to the other terminal. The storage cell, as described
below, is the right size to be charged by a few gravity cells and
is easily ma