Fig. 2. Is a section of the seal. It consists of two metal plates, B B, and D D, having a number of corresponding holes drilled through them, as at _a a a a_, and _b b b b_, into which the ends of small rollers, _a b_, _a b_, are made to fit and turn exactly. When all the holes are supplied with rollers, the plates, B B, D D, are retained at a proper distance by a metal rim, soldered to the edges of the plates. The ends of the rollers being thus exposed, and ground level with the surface of each plate, are to have a groove cut in each, similar to a screw head; this is to be effected by cutting lines from end to end of the plate, as shown at _e e_, _e e_, Fig. 1. With a graver a small dot is next to be made, all to the right on one plate, and all to the left on the other; or, _vice versa_, of each line occupying the small circular end of _each_ roller. It is now evident that, by using a small chisel-shaped steel instrument, or key, with which to turn the roller, the small dotted line on its end, may be so varied as to form any alphabetical arrangement. The position of the dotted line admits of sufficient variety to take in 24 letters, distinct enough to the eye, without increasing the size of the seal. In this alphabet only three variations are supposed to be made from the horizontal and perpendicular, one very slight on either side, the other greater, and the third at an angle of 45°. It only requires a transposition of the letters to produce a correspondence which shall be private between two persons. The use of two faces to the seal is obvious, one serving to compose on, and _the other_, being a reverse, to make an impression on the wax. Were this not the case, a sentence would have to be written from right to left. Its use might be multiplied by making each cipher refer to an entire word or sentence; as, if _a_, stood for men; _b_, for horses; _c_, food; _d_, money; and so forth: a mode which it would be next to impossible for any third party to decipher.--See Mechanics’ Mag. vol. x. 2. How ten thousand Persons may use these seals to all and every of the purposes aforesaid, and yet keep their secrets[5] from any but whom they please. Footnote [5] secrets private. [_Seals private and particular to each owner._] The present is one of those articles of a nature already noticed in the introduction, which can scarcely be classed as an independent invention; it is in fact little, if any, more than some intricate application of the foregoing, a mere step beyond the more obvious employment of such seals. We may consider the first as the instrument, and No. 2 as an ingenious table, by the aid of which to construct alphabets, words, or sentences. 3. A Cypher and Character so contrived, that one line, without returns and[6] circumflexes, stands for each and every of the 24. Letters; and as ready to be made for the one letter as the other. Footnote [6] or--for and.