622 NICHOLLS'S SEAMANSHIP AND NAUTICAL KNOWLEDGE
The one, two, three and four-letter flag hoists are arranged in alpha-
betical order, as also are the chief words of their corresponding phrases
and sentences, so that coding and decoding can usually be made at one
opening of the book. The four-flag signal letters of ships are given in
a separate book entitled The Mercantile Navy List and also in another
book called Signal Letters of British Ships. The top flag of the hoist
indicates the nationality of the vessel; for example, the top letter of
the names of British ships is flag "0" or flag " M."
THE CODE FLAGS.
The set of Code flags consists of 26 alphabetical flags (one for each
letter of the alphabet), 10 numeral pendants (one for each unit 1, 2, 3, 4,
5, 6, 7, 8, 9, 0), 3 substitutes and the Code pendant—40 flags in all
Five new flags have been introduced, C, D, E, F and G, to replace
those letters of the former Code which were represented by pendants;
those pendants, without alteration, now indicate respectively the
numerals 1, 2, 3, 4 and 5 of the new Code with the addition of five
new pendants to make up 6, 7, 8, 9 and 0, the decimal point being
indicated by the Code pendant. A pendant now represents a numeral
only and is referred to as No. 1 numeral, No. 2 numeral, etc., and a
flag represents a letter of the alphabet and is referred to as letter "4"
or letter "B," etc.
Single-letter signals, one for each flag, are either very urgent or
of very common use. A second series of single-letter hoists are towing
signals. See page 636.
Two-letter hoists are mostly distress, urgent and important signals
with the addition of a few general signals of common use. See examples,
pages 636 and 637.
Three-letter signals are general in character and are used for words,
phrases and sentences. See examples, page 637.
Four-letter hoists commencing with the letter "A" are geographical
signals, and four-letter hoists commencing with letter G are the signal
letters of British ships.
USE OF THE SUBSTITUTES,
The substitutes are intended to indicate a repeat of the same flag,
or pendant, in a hoist, so that double or even treble letters or figure*
may be conveyed in the same hoist by one set of flags only.