After all the difference is merely one of degree. Even the widest notion of the broad front, that of Gätke, who insisted, as dogmatically as he did on most points, that the width or breadth of the migrating host corresponded with the extent of the breeding range (29), is of a route, bounded on the one hand by the northern or eastern and on the other by the southern or western lines of latitude or longitude which marked the limits of the range. The idea of a route may be narrowed down to the extent of a wide river valley, or to a fly-line represented on a map by a ruled line, which passes over certain ascertained places. The absurdity of Gätke's arguments are proved by the study of his truly remarkable book. According to him the island of Heligoland was only remarkable in that it possessed an observer, himself, who saw marvels unobserved elsewhere, though the same number of birds were every year passing over any particular spot in an area which, for many species, must have been many degrees in extent. Had not so much weight been placed upon, and so many arguments based on Gätke's extraordinary statements by, unfortunately, many of our leading British ornithologists, his theories might have been ignored. Unfortunately he is looked upon as an authority, even an oracle, whereas, as Dr Allen pointed out, on many points which he treats with great positiveness his knowledge is obviously as limited as the little field which was the scene of his life-long labours (2). Glibly he tells of hooded crows "in never-ending swarms of hundreds of thousands" passing across and for many miles on either side of the island; of "every square foot of the island" teeming with goldcrests, and of "dark autumn nights" when "the sky is often completely obscured" by the migrants, which pass thousands of feet overhead. How did he observe the obscured sky? Indeed he again and again declares that migration passes unseen yet calculates the numbers observed on the darkest nights; the illumination of the lighthouse could not be sufficient to enable him to even guess at the numbers he mentions. After stating that "the whole vault of heaven was literally filled to a height of several thousand feet with these visitors from the regions of the far North," and that a certain east to west passage extended from the Faroes to Hanover, he concludes that "the view--that migrants follow the direction of ocean coasts, the drainage areas of rivers, or depressions of valleys as fixed routes of migration can hardly be maintained."