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Rh off between the intervals of these, does not detract from the more striking phenomenon or lessen the difficulty of explaining it. For, surely, there is a difficulty in explaining how the example of one vast body of birds, soaring forth on the morning flight, should not affect every individual of the still vaster body of which they form a part—the whole occupying, it must be remembered, a small and densely packed area—and why the impulse of the flying birds to fly should, apparently, become uncontrollable in each individual of them at the same instant of time. If we saw soldiers issuing in this manner from an encampment, or performing all sorts of collective movements and evolutions before entering it in the evening (as do the starlings before descending on their roosting place), and yet satisfied ourselves that there were neither captains nor officers, signals nor words of command amongst them, we should probably wonder, and might think the phenomenon sufficiently curious to make it worth study and investigation.

I will take one more example from my notes on wood-pigeons before returning to the flocks of small birds at the stacks.

"A number of wood-pigeons" (this was early on a very cold winter's morning) "have now settled on the elms near me. I am quite still, and they have sat there quietly for some little time. All at once the whole band fly out, to all appearance at one and the same moment, and in a peculiar way, with sudden sweeps and rushes through the air in a downward direction, shooting and zig-zagging across each other with a whizzing whirr of the wings, in much the same manner as do rooks. On account of this peculiar