146 BRITISH BIRDS. 



air with their two wings pointing respectively towards 

 the bow and stern. Thus they advance sideways, the 

 point of one wing leading. Instead of a moving ship a 

 cliff may supply the up-current required. The Gull flies 

 to the bottom of the cliff, is lifted high above it, then he 

 turns and faces the breeze and goes on his way, one of 

 his wings pointing towards his destination. He descends 

 slowly as he goes. 



Sometimes Gulls utilize a very local up-current with 

 remarkable cleverness. Behind a steamer, as it travels, the 

 air rushes down to fill the space just vacated by the vessel. 

 This down-rush of air strikes the water, rebounds and 

 forms an up-current. Gulls, following the vessel, having 

 obtained a certain altitude, will sometimes glide rapidly 

 forward, descending all the while till they nearly touch 

 the water, but their downward-onward glide canies them 

 into the up-current which I have just mentioned and they 

 are at once lifted as if they were nothing but feathers. 

 Thus they regain their altitude and again glide forward 

 and downward. The wings are held rigidly expanded all 

 the while, but occasionally the system works imperfectly, 

 and a stroke with the wings has to be put in. 



Gulls and other birds often perform their evolutions in 

 the air in a spirit of pure sport. Sometimes when the 

 wind blows directly against a cliff. Gulls will fly to the 

 base, get lifted high aloft by the up-draught, then descend 

 to the same place and get another lift. 



(To he continued.) 



