MIGRATION AND WEATHER 91 



the letters indicate the direction of the wind, the 

 figures its speed in miles per hour. The last one 

 in the table, observations made at Brighton on 

 September 20th, is particularly useful. The con- 

 ditions on this date were anticyclonic, and favourable 

 to migration. At 400 feet above the sea the wind 

 was blowing at 5 miles an hour ; at between 5000 

 and 6000 feet its force was 20 miles per hour. What 

 then would happen to a bird leaving Brighton for 

 say the Spanish Peninsula ? If it flew at 20 miles 

 an hour towards the French coast about Dieppe, 

 it would meet the wind blowing at 5 miles an hour, 

 and take between five and six hours to reach the 

 coast, head to wind. If it rose to the height of 

 3000 feet it would meet a wind blowing at the 

 same speed as it was flying, and it could make no 

 headway. If, however, it flew in a south-westerly 

 direction the more it turned westerly the farther 

 it would drift down channel towards Normandy 

 or Brittany, and be carried out to sea ! But this is 

 exactly what would not have happened, for on this 

 date a feeble cyclonic system was approaching 

 from the Atlantic and extending its area of influence 

 over southern England. In the Channel the bird 

 would meet westerly winds which would bring it 

 safely to the Brittany shores, or if it missed them, 

 to the western shores of the Bay, where the wind 

 was actually from the north. I mention this 



