222 ADVANCEMENT OP LEARNINO. [BOOK VI. 



of characters,' wlieel-ciphers,^ key-ciphers,'^ word-cipliers/ <fec. 

 There are three properties required in ciphers; viz., 1. that 

 they be easy to write and read ; 2. that they be trusty and 

 undecipherable ; and 3. if possible, clear of suspicion. For 

 if a letter should come into the hands of such as have a 

 power over the writer or receiver, though the cipher itself 

 be trusty and impossible to decipher, it is still subject to ex- 

 amination and question, unless there be no room to suspect 

 or examine it. 



There is a new and useful invention to elude the examina- 

 tion of a cipher; viz., to have two alphabets, the one of 

 significant, and the other of non-significant letters ; and 

 folding up two writings together, the one conveying the 

 secret, whilst the other is such as the writer might probably 

 send without danger. In case of a strict examination about 

 the cipher, the bearer is to produce the non-significant 

 alphabet for the true, and the true for the non-significant ; 

 by which means the examiner would fall upon the outward 

 writing, and finding it probable, suspect nothing of the 

 inner. ^ 



But to prevent all suspicion, we shall here annex a cipher 

 of our own, that we devised at Paris in our youth, and which 

 has the highest perfection of a cipher — ^that of signifying 



destroys the sense to an ordinary observer, which the first letters and 

 words are intended to convey. Ed. 



' Abbreviated writing, or short-hand. Ed. 



•» Tliis is a kind of dial, on which are drawn the circumferences of two 

 concentric circles, bordered by the letters of the alphabet. Each letter 

 being marked with a sign, we know to what letter of the exterior circle, 

 each of the interior corresponds in relation to its rank in the alphabet. 

 For example, suppose that it had been previously determined that the 

 letter f should represent a, g h, and h c, the receiver of the missive 

 uhould turn the interior circle of the dial round until the a in this circle 

 pointed to / in the exterior, and then in the place of the letters in the 

 note he had received, he would read those which corresponded to them 

 in the interior circle. Ed. 



* The key-ciphers are those figures which explain the latent sense 

 of the letter, and are either conveyed with it, or previously concerted by 

 those who are parties to the communication. Ed. 



y Verbal ciphers are those which represent entire words. Ed. 



■ The publishing of this secret frustrates its intention ; for the ex- 

 aminer, though he should find the outward letter probable, would 

 doubtless, when thus advrertised, examine the inner, notwithstanding itr 

 alphabet were delivered to him for noa-signifioants. Shaw, 



