Is this a case of prevision? Granting that the agreement of the facts with the vision is not due to mere accident, the possibility yet remains of a falsification of memory; that is, the possibility that a vision originally _similar_ to the event afterwards observed, was subsequently taken to be the _same_ as that event. Such obscurations and falsifications of memory are very frequent. Indeed they get to be epidemic, the moment a second factor, that of _expectation_, is added. We need only have a foreboding that something will eventually happen, and we shall inevitably form certain indefinite notions of its particular character. If now the event actually happens, our obliging memory is at once at hand with the lie, '_Exactly_ as I knew before.' 'I told you so,' is the assertion. And it is therefore no accident that in the literature of clairvoyance, the arrival of letters of this or that tenor plays so great a part; for expectation has a broad and acceptable arena in this very connection. The extent to which the falsification of memory and intense expectation take part in the observation which we shall now cite, it would be hardly possible to determine accurately: "On the evening of March 11th, being tired, I was about to go early to my room, when it occurred to me to wait for the last post, already late, that I might not be again disturbed by having the letters brought to my room. I took up the Crystal rather to pass the time than with much expectation of seeing anything; for as a rule, when one is tired, the concentration of attention necessary to Crystal-vision is somewhat difficult to attain. However, I perceived a white object on a dark ground, soon becoming more clearly defined as a letter in a very large envelope torn at the edges, as if not sufficiently strong to hold its contents. Another envelope, of ordinary size, lying at the top, concealed the address, and the writing on the smaller one was too much blurred to decipher. The vision was momentary only, or I might have applied the test of the magnifying glass, which is sometimes, though not always, of use in such cases. I thought it possible that the vision might be merely the result of expectation, but it seemed at least worth while, after making a note of the fact,—my invariable rule whenever possible,—to test its significance. As a matter of fact, the letters were lying on a seat in the hall, showing white against the dark polished wood—placed there possibly by some one leaving the house who had met the postman before he had time to ring. The letters were two,—the lower one, which had burst the envelope, was the size of a sheet of letter-paper not folded, and was for myself, the upper one, the usual size of a note, and not for me, which may have accounted for my inability to read the address." (No. 66.)