a    after     n    not     uc    your
b    before    r    are     w     word
c    can       t    the     wi    with
h    have      u    you     y     yes

These abbreviations saved a lot of time, for when we wanted to signal the word after instead of spelling it out—­22-2221-2-12-211-3—­we used the signal for A—­22—­followed by 3 to signify that it was the end of the word.  Before was represented by 2112-3, your by 111-211-3, etc.  It took quite a little practice to learn the different combinations.  Fred and Reddy soon became experts, and could flash the signals back and forth at a great rate.

[Illustration:  Fig. 151.  The Signal for Letter “B.”]

Wigwagging at Night.

At night we used a torch in place of a flag.  The torch consisted of a roll of dried birch bark tied with wire to the end of a staff.  It was found necessary to place another torch on the ground directly in front of the signaler so as to fix a central point and enable one to determine whether the moving torch was swung to the left or right.  A later improvement was to use three lanterns, one in each hand and one attached to the waist to fix the central position.  It was quite an advantage to have a lantern in each hand, for it saved changing over from one to the other when a second movement followed a first or a first movement a second.

[Illustration:  Fig. 152.  Wigwagging at Night.]

The Heliograph.

The book that Uncle Ed sent us had in it a description of a heliograph, that is, an instrument for sending signals with flashes of sunlight.  Although our wigwagging system was good enough for our requirements, yet we thought it would be more scientific to use the sun instrument, and besides, the latter could be used for signaling many miles.

The Single Mirror Instrument.

[Illustration:  Fig. 153.  Trunnion for Mirror.]

[Illustration:  Fig. 154.  The Single Mirror Instrument.]

The first thing we did was to procure a small mirror about 4 inches square, mounted in a wooden frame.  Then we got a pair of small square head bolts about 1/4 of an inch in diameter and 1 inch long, also two strips of brass 1/2 inch wide and 3 inches long.  In the center of each brass strip we drilled a hole just large enough to admit the shank of one of the bolts, and then the strips were fastened with screws tight against opposite edges of the mirror frame, with the heads pressed against the frame and the shanks sticking out at each side, as shown in Fig. 153.  These projecting shanks served as “trunnions” (that is, pivots) for the mirror to turn on when it was mounted in place.  After the trunnions had been set in place we made a peep hole in the center of the mirror by cutting out a piece of the wooden back of the frame and scratching away the silver from the back of the glass.  Only a very small hole was required, about 1/8 inch in diameter.  Great care was taken to have the unsilvered spot exactly