Chapter IV

On the use of the Wheel, an Instrument to be employed in connection
Especially with Alphabets arranged without regard to Order

I have now presented two kinds of Modes belonging to Simple Transposition.  The search, however, for letters in the lower, or more remote, alphabets is, whenever we proceed according to the last-mentioned Modes, the cause of much inconvenience, and so there have been invented the wheel and wheel-revolving.  The construction of the wheel is carefully set forth by Porta, Bk.2.c.7ff.  Its use is described at length and illustrated by eight figures in Gabriel de Collanges’s Book of Tables, appended to Trithemius’s work on Polygraphy, which de Collanges translated into French.  Briefly, the method of construction is this: Write on a sheet of paper, in the proper order and at intervals to be measured by compass, alphabets such as are contained in the tables, and then attach this paper to a flat piece of wood, hollowed out in the center and on the rim in such a way that a straight edge may be moved back and forth between the alphabets so arranged, after the manner of the instrument constructed by Leonhard Zuber, pt.2,p.54.  On this straight edge, or index, are to be written the letters of the alphabet, in their proper order and at the right intervals.  Now when the wheel has thus been made ready for use, and you wish to obtain a letter from this or that column, move forward the straight edge, and you will be able, with the greatest ease and without mistake, to find and write the required letter.  As the construction is a very easy matter, I have had inserted here simply a figure of the wheel, resembling the figure contained in the aforementioned tables of de Colanges, together with one of the index.