Rock-Borers. 109 
these Rock-borers work their way into and through 
hard stones. Some naturalists assert that they 
effect this by means of an acid which decomposes 
the substance of the rock, and renders it soft; 
others, that the animal keeps turning round and 
round like an instrument called an auger, and so 
eradually rasps away the surface of the stone with 
the angles of its shell, but we question whether 
the shell would not be worn out first in such a pro- 
cess. The generic name of these “ stone-piercers,” 
-comes from the Greek word Pholeo—to hide, and 
the rocky chambers which they hollow out for them- 
selves, are as snug hiding-places as can well be 
imagined; yet however deep they may go into 
these gloomy caverns, as we should be apt to 
suppose them, they need not be in darkness ; for it 
appears that these Pholades emit a most remarkable 
light—whether phosphorescent or not does not 
appear to be determined ; so strong is it, that it is 
said to illuminate the mouth of the person who eats 
the mollusk; and it is remarked by Dr. Priestly, 
that “contrary to the nature of most fish, which 
give light when they tend to putrescence, this is 
more luminous the fresher it is, and when dried its 
light will revive on being moistened with water.” 
So that in more respects than one these Rock-borers 
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