THE RETURN OF THE SWALLOWS. 9 



counties of England ; but this year the spring, in spite 

 of its early promise, has hung fire a little in a curious 

 half-hesitating way : and so I have not seen the first 

 swallow till this morning. The swifts, larger and stronger 

 birds, which fly even more incessantly than their cousins 

 and therefore require a more abundant food-supply, do 

 not usually come northward till the beginning of May, 

 when the flowers and insects are in full force ; and they 

 leave us again in August, while the swallows linger on 

 till the late autumn. Both kinds fly low and open- 

 mouthed over the most flowery meadows, where they 

 catch honey-sucking insects in abundance : or over the 

 ponds and rivers, where they meet with innumerable 

 mayflies and other winged species, whose larvae live as 

 caddis-worms or the like under water, while the perfect 

 insects hover above it to lay their eggs upon the surface. 

 The question as to the supposed instinctive feelings 

 which drive the swallows north or south at the jiropcr 

 season is an extremely interesting one : and perhaps 

 only very recent views as to the nature of climatic changes 

 and zones can enable us in time to give the true explan- 

 ation. Hitherto it has been usual to think of the differ- 

 ences of climate between Europe and Africa as though 

 they had always been permanent, and so to raise un- 

 necessary difficulties in the way of a rational solution to 

 the problem. If England had always had a cold winter, 

 while Algeria always liad a warm one, and if a double 

 belt of sea had always separated us from the two 

 continents, it would indeed be hard to understand how 

 an English bird could first bethink itself of moving 

 southward in winter, or how an Algerian bird could ever 

 be seized with an original impulse to go northward in 



