^°/s9^"] CouEs, Gdike's Heligoland. 323 



established and successfully operated ornithological observatory 

 in the world. Gatke's figure is unique in our annals ; not one of 

 us can remember a time when he has not stood alone for all we 

 know of the subject to which his life has been devoted, like a 

 veritable Pharos, throwing a steady light upon the dense darkness 

 of our ignorance. The veteran is now in his eighty-third year ; 

 he has kept ceaseless watch for half a century ; and this volume 

 gives the ripe fruit of his long vigilance, without a sign of failing 

 powers, with the enthusiasm of youth unabated, with scrupulous 

 fidelity to facts, and with scientific precision of statement. It is 

 one of the most original, most remarkable, and most valuable 

 books ever written about birds. I am sure no reader of ' The Auk ' 

 can fail to be interested, if I succeed in reflecting upon these 

 pages anything like an adequate representation of Gatke's results. 



About one-fourth of the work is devoted to a treatise upon 

 migration in general, as viewed from the Heligoland standpoint, 

 and this is followed by one chapter on color-changes without moult, 

 or what I have called aptosochromatism. The main body of the 

 work is occupied with the systematic consideration of the 397 or 

 398 species which occur or have occurred on this island, the whole 

 record being given in minute detail. I will revert to the first- 

 mentioned matters in the sequel, when we shall find that some of 

 Gatke's results are nothing short of astounding. But first, let us 

 proceed to some analysis of this extraordinary local list. 



To appreciate the situation, we must know that Heligoland is a 

 little island in the German Ocean, due east of the mouth of the 

 Humber in England. It is a mere islet, in fact — a sea-girt red 

 rock of triangular shape, with a flat top and steep sides, practically 

 inaccessible except at one end, where there is a low sand-spit 

 and a broken escarpment; the total length is 5,700 feet, or little 

 over a mile. The rock is bare except for the green turf — so bare 

 that the "throstle bushes," or contrivances made of brush and 

 network to catch thrushes, are among the conspicuous features of 

 the surface. There is a little town, whose buildings are mainly 

 at one corner of the island, and a lighthouse. Such is the scene 

 of Gatke's lifelong labors, to which billions of birds fly regularly ; 

 and among them his watchful eye has found astrays from every 

 quarter of the globe. 



