The horizontal line of letters and the perpendicular column on the other side are Transpositive; the former recording the letters of the General, the latter those of the Particular, alphabet.  The matter is clear; let us, therefore, dispense with examples.

If we fix upon the second method, that, namely, wherein the process is performed with a shortened form of the common alphabet, -- and the alphabet may be shortened by leaving out the less frequent letters, K, Q,W,X, and Y, together with the sign of aspiration H (see c.10 of this Book, near the beginning), --the schemes will then be put into less lengthy form. .This may be seen in the schemes of the third class (of which, directly), in which the alphabet is completed in eighteen letters.

If we choose the third method, and prefer to make use of half as many Stations, then the follwoing scheme is produced:

Here more than half the Stations, or Positions, or the two-letter groups are omitted.  These are obtained by reading in the opposite direction the existing Stations.  Thus, the Position BA is obtained by reading backward the existing Position AB.  The same reasoning and the same method apply to the other omitted Stations.  There are likewise omitted here the letters H,K,W,X, and Y, together with the letter Q, which is used only in the combinations Qua, Que, Qui, Quo,  Quu:.  These have all, for the sake of completeness, been thrown into a single column at the end.  To assist in learning the use of the table, it should be held in mind here that each letter written beneath the column is Transpositive of the first letter met in writing down the secret;