I am most respectfully yours. W. B. TYLER. To Edgar A. Poe, Esq. [Illustration: a cryptograph] The difficulty attending the cipher by key-phrase, viz: that the same characters may convey various meanings—is a difficulty upon which we commented in our first article upon this topic, and more lately at greater length in a private letter to our friend F. W. Thomas. The key-phrase cryptograph is, in fact, altogether inadmissible. The labor requisite for its elucidation, _even with the key_, would, alone, render it so. Lord Bacon very properly defines three _essentials_ in secret correspondence. It is required, first, that the cipher be such as to elude suspicion of being a cipher; secondly, that its alphabet be so simple of formation as to demand but little time in the construction of an epistle; thirdly, that it shall be absolutely insoluble without the key—we may add, fourthly, that, with the key, it be promptly and _certainly_ decipherable. Admitting, now, that the ingenious cryptograph proposed by our correspondent be absolutely what he supposes it, impenetrable, it would still, we think, be inadmissible on the first point above stated, and more so on the second. But of its impenetrability we are by no means sure, notwithstanding what, at a cursory glance, appears to be the _demonstration_ of the writer. In the key-phrase cipher an arbitrary character is sometimes made to represent five, six, seven, or even more letters. Our correspondent proposes merely to reverse the operation:—and this simple statement of the case will do more towards convincing him of his error than an elaborate argument, for which we would neither have time, nor our readers patience. In a key-phrase cryptograph, equally as in his own, each discovery is _independent_, not _necessarily_ affording any clue to farther discovery. Neither is the idea of our friend, although highly ingenious, philosophical, and unquestionably original with him, (since he so assures us,) original _in itself_. It is one of the many systems tried by Dr. Wallis and found wanting. Perhaps no good cipher was _ever_ invented which its originator did not conceive insoluble; yet, so far, no impenetrable cryptograph has been discovered. Our correspondent will be the less startled at this, our assertion, when he bears in mind that he who has been termed the “wisest of mankind”—we mean Lord Verulam—was as confident of the absolute insolubility of his own mode as our present cryptographist is of his. What he said upon the subject in his _De Augmentis_ was, at the day of its publication, considered unanswerable. Yet his cipher has been repeatedly unriddled. We may say, in addition, that the nearest approach to perfection in this matter, is the _chiffre quarré_ of the French Academy. This consists of a table somewhat in the form of our ordinary multiplication tables, from which the secret to be conveyed is so