Charles Wheatstone was interested in codes and ciphers and as part of his recreational activities amused himself by deciphering coded correspondence in the notices of daily newspapers usually sent between clandestine lovers or men concealing matters of business. It may have been the apparent ease of this practice that led Charles to develop “The Cryptograph”.
The Cryptograph uses one of the oldest and simplest forms of encryption – the Caesar cipher named after the roman leader Julius Caesar who used it to protect messages to his generals. The Caesar cipher is a type of substitution cipher which shifts the alphabet a fixed number of characters. However Wheatstone’s Cryptograph is more complex – as the long hand is rotated to each new character to be encrypted or deciphered, a gear to the shorter hand ensures a shift every rotation. This ingenious design circumvented the common method of deciphering the Caesar cipher by analysis of the distribution of alphabet characters (which is how Wheatstone would have decoded that lusty correspondence).