It is seen that the alphabets, both interior and exterior, are reduced in each case to twelve letters.  The question of how this reduction may be conveniently made, I have touched upon above, in c.10.  N omitted at the beginning of a word may here be signified by a point.   The alphabet in the interiro of the table is found three times complete, though, on the basis of Transposition, it appears six times, the arrangement being such that, on each occasion, four letters, each three times repeated, form an alphabet.  Secondly, the exterior alphabet that is prominent at the top offers no difficulty; but, in the case of the alphabet written perpendicularly at the side, it may be noticed that in each exterior square there are written two letters.  Whence it results that each interior letter may stand indifferently for either one of two letters.  The praxis is nearly the same as that of the preceding cases.  We have here the same method of resolving the letters, as well as the same process of making Transposition.  There is this difference, that, since the interior letter, as already said, represents indifferently either of the two perpendicular letters, there must, for the sake of distinction, be written by the side of the lower letter of each square, at every occurrence thereof, a small note to serve as a key in re-transposing: e.g. ss, or ff, or z.  Thus, if a lower letter of the square is to be understood, let there be placed by its side some one of  these notes, and let the process be performed in this simple and uniform manner, or let there be assigned a different note to each square, which shall belong thereto: e.g. to the first square ss, to the second square ff, to the third z, to the fourth x, to the fifth q, and so on.  If, then, we have to write the word Patris, either by itself or with some other word, as, for instance, faciem resolve the letters as already directed.  In this example, it has been found necessary to add the key twice only, the reason being that twice only does a letter from the lower order occur.