CH. XIV] CRYPTOGRAPHS AND CIPHERS 295 



or words of the message are re-arranged in some pre-determined 

 manner. 



One of the most obvious cryptographs of this type is to 

 write each word or the message itself backwards. Here is an 

 instance in which the whole message is written backwards: 



tsop yb tnes tnemeerga fo seniltuo smret ruo tpecca yeht. 



It is unnecessary to indicate the division into words by 

 leaving spaces between them, and we might introduce capitals 

 or make a pretence of other words, as thus: 



Ts opybtne sine meer gafos eniltu Osmret ruot peccaye Jit. 



A recipient who was thus mis-led would be very careless. 

 Preferably, according to modern practice, we should write 

 the message in groups of five letters each: the advantage of 

 such a division being that the number of such groups can be 

 also communicated, and the casual omission of letters thus 

 detected. 



Systems of this kind which depend on altering the places of 



letters or lines in some pre-arranged manner have always been 



common. One example is where the letters which make up 



the communication are written vertically up or down. Thus 



the message : The pestilence continues to increase, might be 



eiotnlit written in 8 columns as shown in the margin, 



sntioeth and then sent in five letter groups as eiotn 



acsncnse litsn, etc. If before reading off the message 



ereuecep. the 8 columns were interchanged according 



to some prearranged scheme the cryptograph would be greatly 



improved, and this is said to be a method used in the German 



Army. This cryptograph might be further obscured by writing 



the 32 letters according to the Route Method described below. 



Another method is to write successively the 1st, 18th, 35th 

 letters of the original message, and then the 2nd, 19th, 36th 

 letters, and so on. If, however, we know the clue number, say c, 

 it is easy enough to read the communication. For if it divides 

 into the number of letters n times with a remainder r it suffices 

 to re-write the message in lines putting n + 1 letters in each 

 of the first r lines, and n letters in each of the last c-r lines, 



