306 Proceedings of the Royal Physical Society. 



to Spain, where, however, the sea rapidly deepens close off 

 shore. 



A reference to the Admiralty charts of the North Sea and 

 British seas will satisfy, I believe, inquirers in the above 

 directions ; or, if a study of these entails too much labour, a 

 glance at a map, reduced from the same, "of the KW. portion 

 of the European Continent during the earlier part of the 

 Glacial Period, showing the land area produced by an uprise 

 of 600 feet above the present sea-level, Snowdon being 

 then 5200 feet high" (which map is contained — as also are 

 the above words I quote — in Professor Eupert Jones' " Lec- 

 ture on the Antiquity of Man," Van Voorst, 1887), will 

 suffice to further explain what I have said. To this part, I 

 have only to add, that a glance at the same map will show 

 that, between the extended line of the 100 fathoms' depth 

 and the coast of Scandinavia a deep trough occurred, which 

 separated the peninsula of ancient Europe from Scandinavia, 

 and into which all eastward- and northward-flowing rivers 

 from the peninsula debouched. The soundings of the Ad- 

 miralty sufficiently localise the positions of these ancient 

 river-beds, even in later years. 



Passing from Heligoland and the Continent now to the 

 Isle of May, I desire to emphasize its relation to the former. 



Heligoland, we have seen, is in Lat. 54° 11' JST., and Long. 

 8° 14' E., and was at one comparatively remote time connected 

 by land communications with the Dogger Banks, Isle of May, 

 and Great Britain. The Isle of May is situated in Lat. 56° 

 11' 22" K, and Long. 2° 32' 47" W., only 2^° K and 12° 9' 

 W. of Heligoland. When the next part of our subject comes 

 under your notice, which it will do immediately, the signi- 

 ficance of these relative positions can scarcely, I believe, be 

 over-estimated. Further, the Isle of May occupies the 

 commanding "key of the Forth," just as Heligoland consti- 

 tutes the key of the Elbe, whether we apply the expression 

 to commerce, war, or to " bird-migrants." 



2. We proceed to speak of the ascertained facts — which 

 may indeed now be termed Laivs — of migration which have 

 been elucidated by our accumulated statistics of the past 

 seven years. These laws of migration, when taken in con- 



