sat on the fence, admitting that it might be possible with some species and probably was with swallows. Later some Americans produced "evidence" in favour of avian hibernation, and even Mr Charles Dixon, in his earlier book at any rate, did not think it impossible (25). The only argument in favour of hibernation is that it is a habit resorted to by other vertebrates to escape the consequence of exposure to severe temperatures. The arguments against it are, that not a single instance of avian hibernation will stand the light of reason and investigation, and that birds are provided with the means of escaping from the cold zone and certainly nee these means. There are flightless birds, but they all live in climates in which they can exist at all seasons. As Seebohm puts it—" The hibernation of birds is a theory, the evidence in support of which has completely broken down. The migration of birds is a fact, as completely authenticated as the fact of their existence."
Dr Derham's "Physico-Theology" appeared in 1737 (24), and contained some sound reasoning about migration, though he was a little puzzled with the many hibernation stories. In 1780 an anonymous pamphlet—"A Discourse on the Emigration of British Birds," flouted the theory of winter sleep in no measured terms (33). This pamphlet was, at first, attributed to George Edwards,
