THE SWALLOW TRIBE. 331 



atmospheric changes, and may well be relied on 

 as giving indications of these in various ways. 

 Nor is it the bird alone, which is thus influenced. 

 All animals, which living entirely in the air are 

 exposed to its variations, are far more cognisant 

 of these changes than we are. Thus the frogs 

 croak in the pool, and the cattle run wildly over 

 the meadow, and eat with unusual voracity their 

 meal from the grass ; the ants bring back the 

 chrysalides to their nest ; the earthworm comes 

 up to the surface, to respire the welcome moisture ; 

 and the very fishes in the pool seem to know that 

 rain is coming, and arise up to the surface. Yet 

 the shepherd cannot feel these changes, though he 

 may observe their prognostics, and see how the 

 leaves of the clover field are standing upright, and 

 the scarlet pimpernel is folding its petals, and 

 hear more clearly the usual sound of some distant 

 sheep-bell, or of some trickling waterfall, as it 

 comes down the slope of the hill. 



We have four species of the Swallow tribe. 

 The Common Swallow [Tlirundo rustica), the 

 Martin {Hirundo uMcd)^ the Sand Martin [Hi- 

 rundo riparia)^ and the Swift [Cyjpselus opus), 

 all alike, in many of their habits, and all coming 



