CHAPTER VI.--_Codes and ciphers.

Codes in use 84 Employment of codes 84 Cipher code 85 The War Department Code 86 Cipher code in field work 87 Field ciphers: Description and use 87 Forms of field cipher 88 Inversions 88 Concealment of terminations 88 Cipher apparatus: The cipher disk 89 The mathematical cipher 93 The route cipher 94 Cipher detection: Employment of cipher disk 96