]02 HOMES WITHOUT HANDS, 



in producing those mighty changes that are continually taking 

 place over the whole face of the glohe. 



We know that although the general proportions of sea and 

 land are maintained, a continual change is being worked in their 

 relative positions. Even within the memory of man, fields now 

 blooming with com were once covered with the salt water, and 

 buildings that were once a mile from the shore are now in hourly 

 danger of falling into the sea. And I have very little doubt but 

 that the Pholas plays a very important part in these changes. 

 If the reader will examine any of our chalk-bound coasts, and 

 will walk from the foot of the existing cliff to the extreme of 

 low-water mark, he will see that the Pholas has everywhere left 

 the tokens of its industry. Even at the verge of low water, the 

 spot whereon he stands was once the base of the cliff which has 

 now receded so far from the waves, and continues to recede 

 yearly. And as he looks out to sea, and watches the breakers 

 fling their white foam over the sunken rocks, and notes the dark 

 masses of tangle lifting with the waves, he sees the remains of 

 former cliffs, that have long since crumbled away piecemeal and 

 fallen into the sea. 



It is tme that the continual dashing of the billows will, in 

 time, destroy the hardest rocks, and that even a granite cliff 

 cannot withstand the action of water. But the process of de- 

 struction — if we may use such a word — is greatly accelerated by 

 the multitudinous holes bored by the Pholas and other buirowers, 

 and the rock is rapidly undermined by the joint action of the 

 molluscs and the waves. The upper portion of the cliff is thus 

 left without support, and when a few heavy rains have loosened 

 the earth, down comes a mixed mass of rock, soil, and herbage, 

 and a fresh face is thus made to the cliff. The loose earth is soon 

 washed away by the waves, the submerged portion of the fallen 

 rock is eagerly seized upon by the burrowers, and in process of 

 time, the whole mass crumbles away, is broken up by the storms, 

 and the fragments are gradually rubbed to atoms by the action of 

 the waves. Thus it is that the cUffs recede on one side, whUe 

 the son advances on another, and so the whole face of the world 

 is gradually changed. 



Perhaps the Date Shells are even more powerful as bui'- 

 rowers than the molluscs which have just been mentioned. One 



