A "wigwag" flag may be easily made by sewing a white square of muslin in the centre of a red bandana handkerchief.
The best method of learning this system is to send simple messages, looking up the letters that there is any doubt about, and correcting mistakes as you go along.
APPENDIX.
NAVY CODE FLAGS.
Messages sent by the navy code flags cannot be read except by the aid of the code book.

There are ten numeral flags--1 to 9, and one for 0.

All messages are made up by means of these ten flags headed by the code flag (whether it be geographical, telegraph, or navy list).
For instance, a line of bunting is sent up on the flagship's signal halliards.

It is read from the top down.

The geographical flag flies first; then follow 7, 6, 3, 8.