Chapter 22
On Mediate or Secondary Transpositions.

The Primary Universal Mode, which is the most far-reaching (see, above, c.1.ad fin.), being disposed of, we come now to the second Mode, called the Secondary, which depends on Mediate Transposition.  This Secondary, or Mediate, Transposition, takes place as follows:  The Power of the alphabet is transferred into as many arithmetical figures as the alphabet contains letters ( a process I will expound more fully below, in c.4 of the next Book), and then, for the figures, are in turn substituted numerical letters, or letters having, either by custom or by agreement, the Power of numbers.  Thus, by custom the following Roman letters signify numbers: I, V, X, L, C, D, M; and by agreement, quite in the manner of the common figures, A stands for 1, B for 2, C for 3, D for 4, E for 5, F for 6, G for 7, H for 8, I for 9, AK for 10, AA for 11, AB for 12, AC for 13 etc, Bk for 20, BA for 21, etc.   The process and Mode is threefold, as in the case of Transposition;  for we may perhaps proceed in this case by the same number of Modes as in the other.

The first Mode is performed thus:  Let the scheme of the Transpositive letters be the following:

If now the word Balneum is to be written, the following form will result: AD.ac.bc.b.ag.i.a.;  or, if one prefer the common Roman numerals, the following: XIV.XIII.XXIII.II.XVII.IX.I.  As the principle is here quite simple, one may, if he care to go farther in the use of this unmodified method of concealment, turn to the first three tables set forth in Chapter Four of the following Book (Book 6), and remember that all the different variations of the alphabetic arrangement there presented answer in changing the value of numbers.  Thus, if the table which I have inserted in c.5, above, from de Vigenere, be again taken in hand, and an application thereof be made according to the method given below, there results a rather elegant Mode of this Mediate Transposition.  The method is this:  First remember that in this case the whole process connected with Transposition is performed by numbers.  This done, select the secret text which you wish to convey to your friend; e.g. the following: Omnium rerum vicissitudo.  Next, take as a key words and an expression such that the letters thereof are about equal in number to those of the secret text, --equal, that is, if the secret is very short; otherwise, the key must be repeated as many times as is necessary.  Let the following words serve as a key:  Omnia conando, vincit omne.  Now arrange the numbering of the letters, both these of the secret sentence and those of the key-sentence, thus