CH. XIV] 



CEYPTOGEAPHS AND CIPHERS 



297 



in the diagram, certain spaces being filled with dummy words 

 «, y, z,..., and the message being sent in the order 11, 8, 13, 2, 

 15, 4, w, x, 1, .... This method was used successfully by the 

 Federals in the American Civil War, 1861—1865, equivalents 

 for proper names being used. It is easy to work, but the 

 key would soon be discovered by modern experts. 



A double cryptograph is said to have been used by the 

 Nihilists in Russia from 1890—1900. Such double transpo- 

 sitions are always awkward, and mistakes, which would make 

 the message unintelligible, may be easily introduced, but if 

 time is of little importance, and the message is unlikely to fall 

 into the hands of any but ordinary officials, the concealment is 

 fairly effective, though a trained specialist who had several 

 messages in it could work out the key. 



Second Type of Cryptographs. A cryptograph of the second 

 type is one in which the message is expressed in ordinary 

 writing, but in it are introduced a number of dummies or non- 

 significant letters or digits thus concealing which of the letters 

 are relevant. 



One way of picking out those letters which are relevant 

 is by the use of a perforated card of the shape of (say) a 

 sheet of note-paper, which when put over such a sheet permits 

 only such letters as are on certain portions of it to be visible. 

 Such a card is known as a grille. An example of a grille with 

 four openings is figured below. A communication made in this 



way may be easily concealed from anyone who does not possess 

 a card of the same pattern. If the recipient possesses such 



