1816.) A New Cypher. 105 
- ArTICLE IV. 
A New Cypher proposed. 
(To Dr. Thomson.) 
SIR, 
To contrive a cypher whieh shall be at once secure from detec- 
tion, and easy in its application, has been considered a problem of 
some difficulty; and if we may judge from the failure of several 
very well contrived attempts, such a cypher is still a desideratum. 
One of considerable difficulty was proposed in Dr, Rees’s new 
Cyclopedia ; but this has been decyphered by Mr. Gage. Another 
cypher, contrived with great ingenuity, was proposed by Professor 
Herman about the year 1750. It was offered with great confidence 
as a challenge for the learned of Europe. It was, however, decy- 
phered a few years after by M. Bequelin, who read a memoir on 
the subject to the Academy of Sciences of Berlin, which was pub- 
lished in their Transactions for the year 1758. ‘This paper contains 
an explanation of the law of the cypher, and is perhaps the most 
elegant specimen of reasoning on this subject which has yet ap- 
peared. It might well be selected as a model for all future inquiries 
of asimilar nature. The two cyphers just alluded to are perhaps 
amongst the most difficult that have been contrived ; but notwith- 
standing their failure, I will venture to propose the annexed as a 
speeimen of a cypher which possesses very considerable advantages 
over either of them. In point of simplicity it yields to none; for 
each character represents a letter; consequently the number of 
characters to be written does not exceed the number of letters. In 
the former of the two cyphers just mentioned each letter is repre- 
sented by two characters; and in the latter one letter is sometimes 
denoted by the combination of three characters, In point of 
security, the cypher which | propose will, J imagine, be found un- 
exceptionable, [tis constructed purposely with a view to defeat all 
the rules of decyphering ; and though the translation of this spe- 
cimen were to be given, yet 1 am convinced the cypher would 
remain secure. With respect to the number of varieties of which 
this cypher admits, it is unlimited; and the key itself may be 
changed with equal facility at every line or at every letter. Com- 
bining such advantages, it might be imagined that this cypher is 
encumbered with laws which would render it too tedious for prac- 
tice. ‘This, however, is by no means the case. When the key is 
known, it is easy to interpret it; and such is its simplicity, that no 
written memorandum of the key need be preserved; for it may be 
written out at any time without scarcely the least effort of the 
awemory. 
C. B. 
Vor. VII. N° If. H 
