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* Extract from ‘Cryptographia, or The Art of Decyphering’, c.1811 *
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* (Catalogue reference: WO 37/9) *
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The General Theory

Proposition 1
The Art of Deciphering is the explanation of secret Characters by certain Rules.

Prop: 2
Every Language has, besides the Form of the Characters, something peculiar in the Place, Order, Combination, Frequency, & Number of the Letters.

Rule 1
In deciphering regard is to be had to the place, order, combination, frequency & number of Letters.

Rule 2
In deciphering nothing is to be left to conjecture where the art shews the way of proceeding with certainty

Prop: 3
In a Writing of any length, the same Letters recur several times.

Rule 3
Writings of any length are most easy to decipher from the frequent recurrence, & combination of the same Letters.

Prop: 4
One word has often some resemblance to another.

Rule 4:
In Writings of length one word is to be compared with another, that their resemblance, & difference may be observed.

Prop: 5.
No word can be without a Vowel.

Rule. 5.
A Word of one Letter is always a Vowel, or a Consonant with an Apostrophe.

Prop: 6.
The Vowels, generally five, are four times out-numbered by the Consonants: the Vowels must therefore recur most frequently.

Rule 6.
The Letters most often recurring are Vowels.

Prop. 7.
Double Vowels, that is the same vowel repeated, as iis, may be pronounced at the beginning of a word, but not double Consonants.

Rule 7.
Double Characters in the beginning of a word are always Vowels.

Prop. 8.
Short words of two or three Letters have two or three Vowels, or one or two Consonants.

Rule 8.
The Vowels are most easily learnt from short words, which are therefore first to be considered by the Decipherer.

If double Consonants (vid.prop.7) are preceded by a single Letter, that Letter is a Vowel.

In Languages abounding in Dipthongs, one Vowel is often conjoined with another.

The Letter that precedes, or follows double Consonants is, if a Consonant, always one of the liquids, l.m.n.r.

The Consonant q is always followed by the Vowel u.

The Letter u may be joined with other Letters as well as with q.

If two different Characters occur, of which the latter is often conjoined with various Letters, & the former is never found either by itself, or followed by any other Letter, those two are qu.

Prop. 14
The Letters qu are always followed by a Vowel, except in a few instances of Proper Names.

One Vowel recurs more frequently than another.

One Consonant recurs more frequently than another.

In the study of this Art, these general Principles are to be, in the first place fully comprehended, because they are to be applied in the explication of all writings, & are in their own nature infallible. But if the Writing be such as admits not of the application of any of these Rules, it may be determined inscrutable.

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