I repeat, then, that I speak of these things only as of coincidences. And farther: in what I relate it will be seen that between the fate of the unhappy Mary Cecilia Rogers, so far as that fate is known, and the fate of one Marie Rogêt up to a certain epoch in her history, there has existed a parallel in the contemplation of whose wonderful exactitude the reason becomes embarrassed. I say all this will be seen. But let it not for a moment be supposed that, in proceeding with the sad narrative of Marie from the epoch just mentioned, and in tracing to its dénouement the mystery which enshrouded her, it is my covert design to hint at an extension of the parallel, or even to suggest that the measures adopted in Paris for the discovery of the assassin of a grisette, or measures founded in any similar ratiocination, would produce any similar result.
For, in respect to the latter branch of the supposition, it should be considered that the most trifling variation in the facts of the two cases might give rise to the most important miscalculations, by diverting thoroughly the two courses of events; very much as, in arithmetic, an error which, in its own individuality, may be inappreciable, produces, at length, by dint of multiplication at all points of the process, a result enormously at variance with truth. And, in regard to the former branch, we must not fail to hold in view that the very Calculus of Probabilities to which I have referred, forbids all idea of the extension of the parallel—forbids it with a positiveness strong and decided just in proportion as this parallel has already been long-drawn and exact. This is one of those anomalous propositions which, seemingly appealing to thought