to which these facts are subjected, we still feel that much remains unrecorded owing to the difficulties of observation. Mr. Dixon forcibly expresses the opinion that migration is largely "a nocturnal drama of the air," and that "a captive balloon floated above some spot where migration is notoriously prevalent, as for instance at Spurn Point on the Yorkshire coast, in the Wash, on the Sussex downs, or, better still, over Heligoland, fitted with a powerful electric search light and various meteorological instruments, would result in priceless information concerning the annual movements of birds is absolutely certain."
Mr. Dixon's hypothesis is that both the northern and southern regions receive their migrants from the equatorial belts, but that "no migratory bird normally crosses the tropics to breed or to winter, in either hemisphere"; and as subsequently expressed, "one set of individuals passing to the Arctic tundras, the other set to Antarctic breeding grounds—from an equatorial winter centre." To make the author's proposition clear, and to accentuate his argument, we must give another quotation:—"We may conclude that the migration of birds in autumn is neither due to a fall of temperature nor a failure of food, although to the casual observer this invariably appears to be the case; but is initiated by a nostalgic impulse to return to certain centres which are in the majority, if not in all, cases associated with that gregarious instinct which in most species is only subservient to reproduction, and in not a few others is equally as strongly developed, as is proved by so many migratory birds breeding in societies and displaying social tendencies right through the summer."
It will be thus seen that the volume is surcharged with new matter, that we fain hope will meet with the candid consideration of naturalists, though perhaps with small chance of general acceptance among ornithologists. In fact, our author almost anticipates "being 'handled without gloves' by some mud-and-torpor-despising bruiser critic for my heresy." This is surely unlikely, for the book is full of facts as well as suggestions, again proves how the new method of enquiry has invaded ornithology, and is written throughout with a felicity of language and sustained advocacy which affords every weapon for the theory except convincement, though this is all that can be expected in a general way when new views are first promulgated.
