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264 "Of the two assemblies on the ground, one is in perpetual motion, birds constantly rising—either singly, in twos or threes, or in small parties—from where they were, flying a little way just above the heads of their fellows, and re-settling amongst them again. Thus no individual bird, as it seems to me, remains where it was for long, though those in the air, at any given moment, form but a small minority, compared with the main body on the ground.

"But the birds composing the other great assemblage keep their places, or, if some few rise to change them, these are not enough to give character to the whole, or even to attract attention. It is curious to see two such great bodies of birds close to each other, and on the same uniform pasture-land, yet behaving so differently, the one so still, the other in such constant activity.

"About 4 a great number of rooks rise from some trees in a small covert near by, and fly towards those on the ground. As they approach the first great body—which is the lively one—the birds composing it rise up, as with one accord, and fly, not to meet them, as one might have expected, but in the same direction as they are flying. So nicely timed, however, is the movement, that the rising body become, in a moment, the vanguard of the now combined troop.

"All these birds then fly together to the other assembly, and whilst about half of their number sweep down to reinforce it, the other half continue to fly on. The flying rooks, however, are not joined by any of those on the ground. How curious it is that, in the first instance, the one whole body of birds