116 THE FLIGHT OF BIRDS 



than most migrants, may sometimes get into the 

 higher current ? If occasionally they make very 

 good times, apparently against the wind, may not 

 the explanation be that they have got into a stratum 

 of air that was moving in another direction ? Mr. 

 Glaisher, as I have pointed out, found that the 

 direction of the wind sometimes changed at a height 

 of no more than 500 feet. A Homing Pigeon, when 

 he is starting, circles upward and takes his bearings, 

 looking out for landmarks in the direction of the cot 

 for which he is yearning, and it is possible that as 

 he rises he may sometimes find a favourable breeze 

 though the lower one is adverse. I suggest this, 

 since a high authority on Homing Pigeons maintains 

 that anticy clonic weather is the important thing, 

 not the direction of the wind. Looking through 

 the best records, however, I find that the low-level 

 wind has been such as to propel the birds and add 

 to their velocity. If they find themselves in a 

 uniform horizontal current travelling in the direction 

 in which they are travelling, there is no reason why 

 they should be conscious of the movement of the air, 

 unless, indeed, they mark the rapidity with which 

 they pass their landmarks on the earth's surface 

 and draw the inference that there is a tail-wind 

 adding its velocity to theirs ! They must, of course, 

 fly faster than the wind, or the air will give them no 

 support. Now, supposing their own efforts give them 

 a velocity of 35 miles an hour and the wind has a 

 velocity of 25, the two together make up the splendid 

 total of 60. At present I say nothing about the 

 question whether birds are able to fly with the wind 

 when it is blowing a gale. Somehow the belief has 



