310 Proceedings of the Royal Physical Society. 



is brought out by our Eeports, and that is as follows ; and 

 which we believe may be stated as an axiom. 



{e) Whilst all along the eastern seaboard of England, 

 which for the greater part of its extent is low-lying, vast 

 flights of Larks, and many other species of migrants, flow 

 on over the land in uninterrupted waves ; on our Scot- 

 tish east coast the waves of the migration are more com- 

 pressed, and flow in narrowed company up the depressions, 

 which are more marked in a mountainous country, or on a 

 rock-bound shore. It is thus that points of special vantage 

 for an observer are supplied by such stations as the Isle of 

 May and Bell Rock at the entrance of the Firth of Forth, 

 and Pentland Skerries at the eastern end of the Pentland 

 Firth. We have, in our last Eeport (copy of which I lay on 

 the table), pp. 6-9, spoken at some length regarding the 

 action of flights of birds on approaching high sea-cliffs, such 

 as those of St Abb's Head, and the greater part of our Scot- 

 tish coast ; and perhaps I may be allowed shortly to quote a 

 passage which will explain our view^s on this subject : 



" Birds in normal migration against a beam wind fly low, 

 and on reaching low-lying seaboard pass on inland without 

 resting. But on approaching high land, say 200 or 300 feet 

 in height, while at night the greatest darkness is ahead of 

 them, and the greatest light to the north or south of their 

 course, during the day time, if the wind is off shore — a 

 beam wind — on approaching the lee shore, they enter upon 

 a calm belt of sheltered air and water, and choose the easier 

 path along shore. According to w^hether the off-shore wind 

 is strong or light will they approach nearer or keep further 

 out ; and at last, so skirting the coast, finally enter upon one 

 of the great open highways of migration. This, which ap- 

 pears almost undoubted, will in great measure account for 

 the invariably slender returns sent in by nearly all the rock- 

 bound stations of the more precipitous portions of the Scot- 

 tish Coast." I may further remark that, as the strongest or 

 central rays of the lanterns in our lighthouses are focussed 

 upon the horizon, when the approaching birds get close in- 

 shore, they are beneath the glare of the lantern, and less 

 influenced by it, when these lanterns are several hundred feet 



