Numerals. Arrivals and departures. Dates. Indorsements. Letter acknowledgments. Requisitions. Telegram acknowledgments. Mails, shipments, and transports. Blanks for future additions as they may be needed. Ranks and grades of officers and men in the Army. Wireless stations of the Army and Navy. (_g_) Alphabetical list of code expressions arranged conveniently for use. When it is desired to transmit some word or expression not to be found in the code and no suitable synonym can be discovered the word or expression should be sent in plain language or spelled out by the equivalents for letters and endings to be found on page 589. Complete instructions for the use of the code either as a code or cipher are contained in the introductory pages of the book. CIPHER CODE IN FIELD WORK. The use of cipher code in enciphering field messages will usually be practicable only between the several headquarters and other large stations supplied with code books. This method, too, is prohibitive for urgent messages when the time of enciphering and deciphering is an important factor connected with delivery. FIELD CIPHERS. _Description and use._--Field ciphers include all systems and the apparatus connected therewith which are ordinarily employed in enciphering and deciphering field messages. Field ciphers are intended for use when code books are not available, and hence the employment of cipher code is precluded. Some methods of field cipher employ simple forms of apparatus, while others require the use of no apparatus at all. _Forms of field cipher._--There are two general classes of field cipher. The first class employs the transposition or reversal of the letters or words of a message according to some preconcerted rule as a means of secrecy. The route cipher hereafter described is an example of this class. The method used in ciphers of the second class consists in the substitution of certain letters or symbols for each of the individual letters composing the words of the message. Both classes of cipher can be rendered more efficient by a judicious use of inversions and by the concealment of terminations. _Inversions._--By the inversions of the whole or certain parts of messages, according to some preconcerted arrangement, the complications of cipher can be greatly increased. If a message is to be inverted, either as a whole or by clauses, it should be inverted before the cipher letters are written over it. Messages may be further complicated by sending the letters of each word backward in various other prearranged combinations.