362 THE ZOOLOGIST. 



from reports, had previously appeared to them exaggerated and 

 well-nigh incredible. So far from this being the case, they were 

 enabled to confirm by personal observation what they had formerly 

 accepted only upon trust. Amongst others who thus journeyed 

 to Heligoland to satisfy their curiosity was Mr. Henry Seebohm, 

 who in his most interesting work, ' Siberia in Europe/ published 

 in 1880, has given a graphic account of his visit to Herr Gatke, 

 and of all he saw during his sojourn on the island. At page 249 

 of the volume just quoted he writes : — 



11 The modus operandi of migration has been to a large extent 

 misunderstood. Few birds migrate by day. By far the greater 

 number of species migrate by night. The number of places 

 where nocturnal migrations can be systematically observed is very 

 small. Two circumstances are requisite to make such observa- 

 tions successful. First, a sufficiently large population sufficiently 

 interested in the event to permit no nocturnal migration to pass 

 unobserved. Secondly, a sufficiently intelligent naturalist to 

 record the sum of many years' observation. Probably in no place 

 in the world are these desiderata so exactly fulfilled as upon the 

 island of Heligoland." 



Heligoland is a very small place, probably not much more 

 than a hundred acres in extent. It is an isolated triangular rock 

 of red-sandstone, with perpendicular cliffs two or three hundred 

 feet in height, dropping into a sea so shallow that at low-water 

 one may scramble round the island at the foot of the cliffs. Most 

 of the surface of this rock is covered with rich soil and grass. 



About a mile from the island is a sandbank, the highest 

 portion covered over with esparto-grass, and the lower portions 

 covered by the sea at high tide, reducing the island from perhaps 

 fifty acres to twenty -five. 



The resident birds on Heligoland and Sandy Island probably 

 do not exceed a dozen species ; but in spring and autumn the 

 number of birds that use these islands as a resting-place during 

 migration is so large that as many as 15,000 Larks have been 

 known to have been caught there in one night, and the number 

 of species of birds obtained on these two small plots of land 

 equals, if it does not exceed, that of any country of Europe. 



There are many species of Siberian and American birds which 

 have never been obtained in any part of Europe except upon the 

 island of Heligoland, 



