“A system of signals of thirteen flags, which I once saw, was able, by using only four flags at a time, to form nearly fourteen thousand combinations. I will show you how to form numbers with the flags in the print.
Hoist flag No. 7, and it will stand for 7.
Hoist it with the 1st substitute under it, and the two will stand for 77.
Hoist these with the 2nd substitute under them, and they will stand for 777.
Hoist all these with the 3rd substitute under them, and they will stand for 7777.”
“How very curious! We never saw anything like this before.”
“There are methods also of changing the signals, to prevent an enemy from deriving any advantage if the general signal-book should fall into his hands. The rapidity with which signals are given and repeated by different ships is astonishing. Up goes a flag, hoisted by the Admiral, rolled round like a ball; when it has reached the mast-head it bursts out, and in a twinkling at the mast-head of other vessels you see the same signal floating in the breeze.”
“How is it that they can manage this so cleverly?”
“Practice and good telescopes will do wonders. And then the signal-officers, from the state of things around them, know beforehand the flags which are most likely to be wanted. You may form some notion, now, of ships being able to talk one with another, when you see that thirteen flags can send near fourteen thousand messages. There are several plans by which soldiers may talk one with another with their muskets.”