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216 flight, which seems to be joyous and sportive, I do not believe they have seen me. But whether they have or not, the absolutely simultaneous flight of the whole body is, to me, equally hard to account for. Supposing—what would be most likely—that only one bird has seen me, how has this knowledge been communicated, instantaneously, to all the rest? There was no note uttered of any kind. I must have heard it, I think, if it had been, so near as I was, nor are pigeons supposed to have an alarm-note. It may be said that the sudden abrupt flight of one alarmed the rest, but all cannot have been looking at this one at the same time, and it is difficult to suppose that there was anything to discriminate in the actual sound of the wings—for one or more than one bird may, at any time, fly eagerly off without affecting the others. Moreover, if this were the explanation, there would have been an appreciable interval of time between the flight of the alarmed bird and the others, which, to my sense, there was not. But, as I say, I do not believe that the birds saw me, and, if not, the collective, instantaneous impulse of flight seems still harder to account for on ordinary known principles. It is, of course, easy to give a plausible explanation of a thing and take for granted that all the facts are in accordance. But the facts, when one watches them, are apt to discredit the theory. Observation and difficulties begin, often, at the same time."

Returning now to the little winter collections of chaffinches, greenfinches, bramblings, etc., which come and feed at the corn-stacks during the winter, in general they whirr up every three or four minutes, but the intervals vary, and may be much longer.