need of a sending helix, as
close tuning will be hardly possible; but for the stationary set this
is very useful.

The helix is made by building a drum with square heads fastened
together by six or eight uprights, arranged on the circumference of a
circle. On this then are wound ten or twelve turns of No. 10 or 12,
brass or copper wire. Binding posts are fastened to the ends of the
wire and variable contact made on the turns by means of metal spring
clips.

The spark gap is made of a hard-wood base with two uprights to which
are fastened strips of brass. Under these strips are {214} placed two
pieces of battery zincs so as to make the gap between their ends
variable. Binding posts are fastened to the strips for contact.

The sending condenser is the same as the receiving in construction,
but different in material. The dielectric is glass while the
conducting surfaces are tin-foil, arranged in a pile of alternate
sheets of glass and foil. The foil is shaped as in drawing and
alternate sheets have their lugs projecting on opposite sides, all
lugs on same side being connected together. For a one-inch coil but a
few of these plates are needed, but for higher power a greater number
are necessary.

[Illustration: Wireless Telegraph Set Designed for Boy Scouts of
America by L. Horle.]

All that now remains is the setting up of the instruments. They are
arranged as in the drawing, a double-point, {215} double-throw switch
being used to switch from sending to receiving.

After having connected up the receiving instruments, the receiver is
placed at the ear and the point of the detector placed on the various
parts of the mineral until the signals are heard clearly. Then the
tuning coil is adjusted until the signals are loudest.

The sending apparatus is set up, the key and batteries having been
bought or made, and used to call some other station. The clip is put
on various twins of the helix until the other station signals that the
signals are loudest. The station is then ready for actual operation.

NOTES

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Notes

{217}

Notes

{218}

Notes

{219}

CHAPTER V

HEALTH AND ENDURANCE

_George J. Fisher, M. D.
Secretary, Physical Department International Committee
Young Men's Christian Association_

Fitness

Two things greatly affect the conditions under which a boy lives in
these days. One is that he lives in-doors for the greater part of the
time, and the other is