The number of contrivance s which have been or may be adopted, for the convey ance of secret intelligence, seem capable of unlimited variation, according to the acuteness of the contrivers. Pantomimic gestures are practised by every one, and are usually carried to such an extent, that we forget that the perform ers in this description of comedy have no oral communication. The expedients of a knotted string, which, when stretched out, shall apply to letters or words upon a gage possessed by the receiver : the scytale of Lysander, or slip of parchment, containing writing which became legible when wrapped round a staff : the ela borate invention of Ilystixus, who pre tended to cure a servant of sore eyes by shaving his head, and writing his secret upon the scalp with a scarifying instrument, after which the man being confined till his hair had grown, this ex traordinary epistle became in a fit state to be forwarded, along with its bearer, to the place of destination. s These, and many others of sufficient note in histo ry, as well as the events of common life among smugglers and others, mani fest a variety of instances of the secret conveyance of small parcels, such as parchment, paper, cambric, lace, and the like. A pye, or a bottle of wine or beer, small casks of pickles or provi sion; the interior of the construction of saddles, of shoes, or other parts of wearing apparel ; a false skin laced up on a dog : the intestines of a living ani mal, or of the human subject employ ed in swallowing a small receptacle, containing a letter, to be afterwards evaculated.—This short list of vehicles may point out how extensive the gene ral means of secret communication may be made.
We shall conclude the present arti cle, which would require a volume to do it justice, by mentioning two other modes of communication with a consi derable degree of secrecy, though they are perhaps liable to the objection of slowness in the writing. The first con sists in the use of a dictionary, or other work, which must he paged through out, and, if convenient, the lines should be counted : but this last necessity may be supplied by means of a scale, or slip of parchment, with lines and numbers from top to bottom, which may be ap plied to any page, when wanted for rea dily counting the lines. The correspon dents being each provided with the same edition of the same work, the writer is to complete his letter in the usual manner ; but, instead of sending off that copy, he sends another, wherein, instead of the words, he writes for each the page, line, and numerical situation in the line, of each word. The correspondent will therefore, discover them by seeking in his dictionary, or printed work. It will easily be seen that this method amounts to the samt2 thing, as if an index locupletissimus ire made of the author to the minuteness here mentioned, and one of the numeral indications were to be put down in each instance instead of the word itself. The
other method consists in the use of a piece of parchment, ruled with lines cor responding with other lines upon the pa per upon which the letter is to be written. Holes are cut through the parchmenthere and there upon the lines. The parchment thus prepared being laid upon the paper, the letter is to be written through the holes ; after which the paper is to be un covered, and the remaining spaces be tween the words filled with other matter, so as to make a significant letter. The true letter can therefore only be read by a correspondent in possession of a parch ment exactly like the original.
Upon this contrivance it may be re marked, that it is crude and inartificial ; and that it supposes the writer to possess sufficient ingenuity and talent to make a rational and clear letter by filling the spaces, and also that he has so much com mand and management of his pen, as that the secret words shall not be discovered by some crookedness in the ,,line, crowd ing of the space, difference in the pen or ink, or some other circumstance attendant on the writing. In the event of these or any other failure, the letter will be liable to suspicion. It is true, nevertheless, that themethod of n riling byinterposed words may be rendered less objectionable, by placing the significant parts at certain in tervals among the others ; not by mea sure,but by reckoning from the beginning according to some agreed rule ; and in this method the objections with regard to penmanship will be done away by writ ing the letter over again, after it has been once completed.
The method of secret writing by trans parent or invisible inks has been little used in realbusiness, and is entitled to no confidence. This process is effected by using a transparent or dilute solution of some ingredient which becomes colour ed by the action of heat or light, or of some other ingredient. Thus, if a letter be written with a dilute solution of sul phate of iron, or green copperas, it will be invisible when dry : but if the paper be wetted by a feather dipped in the infusion of galls, the writing will become black ; or if the prussiate of potash he used instead of the galls, the letters will be blue. The objection to sympathetic inks is, that the writing becomes visible spontaneously after a short time, and that most of them are rendered visible by the application of any metallic solu tion, or simply by holding them to the fire till the paper is a little scorched. When a secret ink is used, it is advisable, in order to prevent suspicion, that a com mon letter should be written with the or dinary ink between the lines. See Ilse, and also DECYPILERING.