BIVALVE MOLLILSCANS. 215 



that are erected upon piles did an animal, with 

 the boring powers of the ship-worm, enter our 

 rivers and abound there, we should see the mag- 

 nificent bridges that so much adorn our metro- 

 polis and are so indispensable to its inhabitants, 

 gradually go to ruin the vast stones with which 

 they are built might become the habitation of 

 pholads, and other rock-borers, and the com- 

 munication between the two sides of the river 

 greatly interrupted. But a merciful Providence 

 has so limited the instincts of the different 

 animals it has created, that they cannot overstep 

 a certain boundary, nor extend their ravages 

 beyond the territory assigned to them. The law 

 laid down to the ship-worm is to hasten the 

 decay of timber, that is out of its place, and 

 may be denominated an unsightly encroachment 

 upon the ocean this is the law they must obey, 

 and they make no distinction, whether it is dis- 

 owned by all, or an important and valuable part 

 of man's property. Their individual object, as 

 has been stated above, is their own benefit, and 

 they neither know that they obey a law of God, 

 or injure man, but the Almighty by an irresistible 

 agency impels them to it, and they fulfil the 

 purposes of his Providence, at the same time that 

 they provide for their own welfare. 



The history of none of the boring bivalves is 

 more interesting than that of the Pholads, or 

 stone-borers. These animals are defended by two 



