364 SEASIDE DIVINITY. 



suit of fish. This power of penetrating to so 

 great a depth beneath the surface is rendered all 

 the more marvellous when the extreme buoyancy 

 and lightness of the bird are considered. The 

 gannet floats very high in the water, differing in 

 this respect from some aquatic birds, whose bodies 

 when they are swimming are almost wholly im- 

 mersed, so that only the neck and head seem 

 to be raised above the surface. Now the cause of 

 the extreme lightness of the gannet's body has 

 been ascertained by anatomists. It appears that 

 a system of air cells exists both along the sides 

 and the inferior part of the body, and that these 

 all communicate with each other, and can be 

 completely inflated at the will of the bird. It 

 also appears that there exists an air cell in the 

 front of the breast four inches in diameter, in 

 direct communication with the lungs, which the 

 bird can inflate in an instant. Over all these air- 

 vessels, however, a system of muscles are stretched, 

 by means of which the gannet can in a moment 

 press upon the vessels, and completely expel the 

 air they contain. When afloat, therefore, or 

 when flying aloft, the gannet inflates all these 

 air vessels. x The specific gravity of its body is 

 thus reduced, and it swims high on the wave, or 

 soars with comparative facility in the air. On 

 perceiving its prey, however, and darting down 

 upon it, the air-vessels are immediately com- 

 pressed, the size of the bird becomes greatly 

 reduced, its weight and specific gravity are in- 

 creased, and these circumstances, united with the 



