it is below.  They have no variation of principle in their investigations; at best, when urged by some unusual emergency — by some extraordinary reward — they extend or exaggerate their old modes of practice, without touching their principles.  What, for example, in this case of D—­, has been done to vary the principle of action?  What is all this boring, and probing, and sounding, and scrutinizing with the microscope and dividing the surface of the building into registered square inches — what is it all but an exaggeration of the application of the one principle or set of principles of search, which are based upon the one set of notions regarding human ingenuity, to which the Prefect, in the long routine of his duty, has been accustomed?  Do you not see he has taken it for granted that all men proceed to conceal a letter, - not exactly in a gimlet hole bored in a chair-leg — but, at least, in some out-of-the-way hole or corner suggested by the same tenor of thought which would urge a man to secrete a letter in a gimlet-hole bored in a chair-leg?  And do you not see also, that such recherchés nooks for concealment are adapted only for ordinary occasions, and would be adopted only by ordinary intellects; for, in all cases of concealment, a disposal of the article concealed — a disposal of it in this recherché manner, — is, in the very first instance, presumable and presumed; and thus its discovery depends, not at all upon the acumen, but altogether upon the mere care, patience, and determination of the seekers; and where the case is of importance — or, what amounts to the same thing in the policial eyes, when the reward is of magnitude, — the qualities in question have never been known to fail.  You will now understand what I meant in suggesting that, had the purloined letter been hidden any where within the limits of the Prefect’s examination — in other words, had the principle of its concealment been comprehended within the principles of the Prefect — its discovery would have been a matter altogether beyond question.  This functionary, however, has been thoroughly mystified; and the remote source of his defeat lies in the supposition that the Minister is a fool, because he has acquired renown as a poet.  All fools are poets; this the Prefect feels; and he is merely guilty of a non distributio medii in thence inferring that all poets are fools.”

“But is this really the poet?” I asked.  “There are two brothers, I know; and both have attained reputation in letters.  The Minister I believe has written learnedly on the Differential Calculus.  He is a mathematician, and no poet.”

“You are mistaken; I know him well; he is both.  As poet and mathematician, he would reason well; as mere mathematician, he could not have reasoned at all, and thus would have been at the mercy of the Prefect.”

“You surprise me,” I said, “by these opinions, which have been contradicted by the voice of the world.  You do not mean to set at naught the well-digested idea of centuries.  The mathematical reason has long been regarded as the reason par excellence.”