But White seems finally to have persuaded himself that at least a few swallows passed the winter in England in a torpid state--if not in the bottom of streams or ponds, then in holes in their banks. He reasoned from analogy, though he had expressed his distrust of that mode of reasoning. If bats, insects, toads, turtles, and other creatures can thus pass the winter, why not swallows? On many different occasions, during mild days late in the fall and early in the spring, he saw house-martins flying about; the weather suddenly changing to colder, they quickly disappeared. Bats and turtles came forth, then vanished in the same way. White finally concluded that the mystery was the same in both cases,--that the creatures were brought from their winter retreats by the warmth, only to retire to them again when it changed to cold. If he had adhered to his usual caution he would have waited for actual proof of this fact,--the finding of a torpid swallow. He made frequent search for such, but never found any. This notion so long current about the swallows probably had its origin in two things: first, their partiality for mud as nesting material; and secondly, the habit of these birds, after they have begun to collect into flocks in midsummer, preparatory to their migrations, of passing the night in vast numbers along the margins of streams and ponds. White knew of their habits in this respect, and wanted to see in the fact presumptive evidence of the truth of the notion that, though they may not retire into the water itself, yet that they “may conceal themselves in the banks of pools and rivers during the uncomfortable months of the year.” One midsummer twilight in northern Vermont I came upon hundreds of swallows--barn and cliff--settled for the night upon some low alders that grew upon the margin of a deep, still pool in the river. The bushes bent down with them as with an over-load of fruit. This attraction for the water on the part of the swallow family is certainly a curious one, and is not easily explained.