signal, and that these are followed by those nearest to them, and so on till the whole are in motion, then two other difficulties arise, neither of which seems easy to get over. For, in the first place, the birds do not, in many cases, appear to rise in this manner, but, as in the instances here given, simultaneously, or, at least, with a nearer approach to it than any process of spreading, such as here supposed, would seem to admit of; and secondly, it is difficult to understand how, if this were the case, any bird—or, at least, any few birds—could fly up without putting all the others in motion. Yet, as I have mentioned, birds in twos or threes, or in small parties, were constantly rising and flying from one place to another in the assemblage of which they formed a part, whilst the vast majority remained where they were, on the ground. This fact offers an equal or a still greater difficulty, if, dismissing the idea of there being a recognised leader, we suppose that any bird may, for the moment, become one by taking the initiative of flight, or otherwise. And even if we assume that any of these explanations is the correct one, in the case of a whole body of rooks taking sudden flight, or directing their flight to any particular place, or with any special purpose, what are we to think when half, or a certain number of the band does one thing, and the other half another, each, apparently, with equal spontaneity? We are met here with the same difficulties—and perhaps in a still higher degree—as in the case of the flocks of small birds at the stacks in winter.
"If rooks follow and obey a leader, one might expect them to do so habitually, at least in their
