Summer Birds of Passage. 467 
This deliberate manner of travelling re- 
lieves the theory of migration from one of its 
principal difficulties. For this supposition 
makes an easy task of along journey to-those 
birds of passage which are not remarkable for 
agility and power of wing; such as the red- 
start, the yellowwren, the nightingale, and 
other species. These wandering birds are not 
required by the theory, to fly with the greatest 
expedition through 40 or 50 degrees of lati- 
tude, from their winter quarters to their sum- 
mer haunts. On the contrary, one of them 
has been proved to move slowly from one 
station to another, as the sun advances in his 
return towards the tropic of Cancer. The 
winter labours of the jack-snipe, which is re- 
markable for its inactive habits, confirm the 
foregoing supposition. For this bird quits the 
northern regions early in autumn; and, in 
spite of its natural feebleness and indolence, 
makes a shift to travel over the greatest part of 
Europe in the cold season. 'The woodcock also, 
after leaving the same summer retreats makes 
a similar journey, and passes over into Africa. 
I shall now proceed to give a few points 
in the vernal course of the chimney swal- 
low (Hirundo rustica,) which is known to 
tvavel in the spring from Senegal, in lati- 
tude 16° north, to Drontkeim, in latitude 64° 
3N2 
