20 REPORT ON THE MIGRATION OF BIRDS. 



striking the glass, or never being seen hovering round the light. 

 Certainly, returns show a preponderance of deaths or other records, 

 first, at lig]itsJ(ips (the average height of the lights of which above 

 the sea is only a few feet) ; secondly, at such stations — upon 

 isolated rocks — as the Bell Rock, Dhuhcartach, or Skerryvore 

 (the lanterns of which are not more than sixty or seventy 

 feet above the water) ; and a great preponderance above such 

 stations as Cape Wrath (which is 400 feet above the sea) or other 

 similarly elevated lights. During the daytime, whilst crossing 

 towards the English coasts and past the lightships, flocks are 

 usually seen flying low ; and across the Firth of Forth and other 

 narrow estuaries the same thing is observed. At times birds are 

 seen passing high in air " almost beyond the range of vision," 

 and when clouds or fogs rapidly lift or clear off during the 

 time of migration, the said migration appears often to "cease 

 to mortal vision," indicating, some say, a reascent to higher 

 levels. Birds also are known to descend upon Heligoland 

 almost 2)erpendicularly from the sky, indicating, it is presumed, 

 a course of migration at a great height, and a descent there- 

 from upon fog- or haze-covered land to rest or feed. To 

 birds passing through the air above, a local fog beneath pro- 

 bably indicates laud in the midst of icateVj and, if this be 

 so, hence a descent upon it. The various numerical returns 

 of those killed at lanterns are probably a good deal dependent 

 on the heighii at which birds fly in foggy weather. We might 

 call this the vertical area of birds' migration flight as opposed 

 to lateral area. 



Now it seems that light-vessels always return the best-filled 

 schedules, and therefore a preponderance of birds are noticed all 

 along the East English Coast, where light- vessels are most 

 abundant. Whilst upon the East Scottish Coast the returns 

 are infinitely smaller where there are no light -vessels, but only 

 lighthouses, whose lanterns are at a greater height; and the 

 question very naturally arises, "If the Scottish coasts were 

 lighted with light-vessels, would^not the number of records be 

 very considerably augmented?" 



