546 THE OYSTER. 



ing the greatest blessing of life ; for the pressure of air 

 upon their lungs, at the bottom of the water, is too 

 powerful for the human frame to sustain ; and a spit- 

 ting of blood is universally the effect. 



The unfortunate objects selected for this employment 

 arc always those young men Avho appear to be in the 

 highest health ; and it is said that the best divers will 

 continue three quarters of an hour under water ; but 

 many find one quarter completely exhausts their strength. 

 Every diver descends perfectly naked except a net fast- 

 ened round his neck for the purpose of receiving the 

 oysters, and is let down by a rope with a stone fastened 

 to it, which does not weigh less than fifty pounds. 



OF MULTIVALVE SHELL-FISH. 



To view the external habitations of these animals, it 

 is scarcely possible to conceive they contained any 

 thing with life ; yet, what is more extraordinary, they 

 are capable of moving forward with celerity, and, when 

 pursued, frequently escape. 



Of the multivalve shell-fish there are two species, the 

 one of which is stationary, and the other possessing 

 powers which enable it to move ; the latter are distin- 

 guished, in the cabinets of the curious, by the appella- 

 tion of sea-eggs ; but Naturalists have given them the 

 name of sea-urchins, and the former that of the file-* 

 fish. 



The sea-»urchin bears some resemblance to the husk 

 of a chestnut, or a turnip stuck completely full of pins, 

 and upon these pointed angles it proceeds with a de- 

 gree of dexterity which it is hardly possible to suppose 

 such an uncouth form could attain. The mouth of the 

 sea-urchin is placed downwards, and in it may be 

 plainly discerned five teeth : the shell is a hollow vase, 



