"Those who delight in puzzles can find much to ponder here." — Science News Letter "Will be well received by anyone really interested in the subject." — Scientific Book Club Review Readers interested in secret writing will find this book an excellent elementary explanation of transposition and substitution ciphers, codes, and their solutions. More than 150 problems provide practical application as well as tests of skill and ingenuity. After a brief description of the history of secret writing, the reader is introduced to fundamental principles of ciphers — transposition and substitution — and given an understanding of the various methods of enciphering and deciphering secret messages. The author covers geometrical patterns, route transcription, columnar transposition, and other methods used in transposition; under substitution, he treats mixed cipher systems, single-alphabet and polyalphabetical substitution, mechanical devices, the Vigenère system, etc. A discussion of cryptanalysis leads the reader into 151 problems for which answers are provided at the end. Appendixes offer notes on enciphering Japanese; and explanation of the Baconian Biliteral Cipher; frequency tables for English, French, German, Italian, and Spanish.