ches away, and following up the spot on the paper until it reached the
disk.

HELIOGRAPH SIGNALING.

[Illustration: Fig. 160. Top View, showing position of Mirror and
Shutter.]

When at last we succeeded in properly focusing the mirror Bill pressed
the key down three times, sending three quick flashes to Jack as a
signal that he was ready to begin. Reddy wigwagged back O. K., and then
the first heliographic message was sent from the ledge to the island. It
was a rather mixed-up message, and kept Jim and Reddy wigwagging back
and forth very strenuously to straighten matters out. It was my duty to
keep the mirror focused. As the sun moved across the sky the shadow spot
would move off the disk, and I had to keep shifting the mirror to bring
the spot back where it belonged. We used the International Telegraph
Code, which we had been studying every evening for a week, but it was
many weeks before we learned how to use it correctly, even slowly. The
International Telegraph Code is as follows:

A .- B -... C -.-. D -..
E . F ..-. G --. H .... I ..
J .--- K -.- L .-..
M -- N -. O ---
P .--. Q --.- R .-.
S ... T - U ..- V ...- W .--
X -..- Y -.-- Z --..
1 .---- 2 ..---
3 ...-- 4 ....- 5 .....
6 -.... 7 --... 8 ---..
9 ----. 0 -----

The three short flashes Bill sent represented the letter S, which stood
for the word "signal." A was formed by a short flash followed by a long
flash; B by a long flash followed by three short ones, and so on. The
key was held down three times as long for the long flash as for the
short one. We found the best way of learning to send the signals
properly was to count 1 for each short flash, and for each pause between
parts of the letter, and 3 for each dash and for each pause between
letters. Between words we counted 6. Thus, for the letter A the key
would be down when we counted 1, up when we counted 2, down while we
counted 3, 4, 5, and up while we counted 6, 7, 8, for the pause after
each letter. It was rather a confusing code, I admit, but in time we
mastered it, all but Reddy and Fred, who never would learn, but instead
used the wigwag code, letting a short flash stand for 1, a long flash
for 2 and a double long flash for 3.

THE DOUBLE MIRROR INSTRUMENT.

[Illustration: Fig. 161. The Double Mirror Instrument.]

[Illustration: Fig. 162. Top View, showing position of the Two Mirrors
and the Screen.]

Our heliographing instrument did excellent service s