Should this not be considered _perfect_, (though I suspect it would puzzle even the ingenious editor to detect its meaning,) I shall give another method below, which I can show _must_ be, and if I am successful I think you will do me the justice to admit that “human ingenuity” has contrived “a cipher which human ingenuity cannot resolve.” I wish to be distinctly understood; the secret communication above, and the one following, are not intended to show that you have promised more than you can perform. I do not take up the gauntlet. Your challenge, I am happy to testify, has been more than amply redeemed. It is merely with an incidental remark of yours, that I am at present engaged, and my object is to show that however correct it may be generally,—it is not so universally. Agreeably to a part of my foregoing definition, _that_ cannot be a proper cryptograph, in which a single character is made to represent more than one letter. Let us for a moment see what would be the result if this was reversed,—that is, if more than one cipher were used for a single letter. In case each letter were represented by two different characters, (used alternately or at random,) it is evident that while the certainty of reading such a composition correctly, by help of the key, would not be at all diminished, the difficulty of its solution without that help, would be vastly increased. This then is an approach to the formation of a secret cipher. If, now, the number of the characters were extended to three or four for each letter, it might be pronounced with tolerable certainty that such a writing would be “secret.” Or, to take an extreme case, a communication might be made, in which no two characters would be alike! Here all reasoning would be entirely baffled, as there would evidently be no objects of _comparison_; and even if half a dozen words were known, they would furnish no clue to the rest. Here, then, is a complete _non plus_ to investigation, and we have arrived at a perfect cryptograph. For, since any given cipher would stand for but one letter in the key, there could be but a single and definite solution; and thus both conditions of my definition are fully satisfied. In the following specimen of this method, I have employed the Roman-capital, small letter, and small capital, with their several inversions, giving me the command of 130 characters, or an average of five to each letter. This is to “make assurance doubly sure,” for I am satisfied that were an average of three characters used for each letter, such a writing would be emphatically secret. If you will be so kind as to give my cipher a place in your interesting Magazine, I will immediately forward you its key. Hoping that you will not be displeased with my tedious letter,