98 



GEOLOGY. 



away, standing up in the midst of the water, look in the 

 distance like fleets of vessels. On the coast of France, 

 especially in Brittany, where the tides rise to a great 

 height, the sea is constantly encroaching upon the land, 

 and occasionally does so to a large extent. In the ninth 

 century many villages were carried away. Great changes 

 have occurred in Holland from time to time, the land 

 sometimes gaining upon the sea, and sometimes the re- 

 verse. At one time the tide, breaking through a dam, 

 overflowed seventy-two villages, and irretrievably de- 

 stroyed thirty-five of them. Other examples in abund- 

 ance might be cited, but these will suffice. 



182. Erosive Power of Water. Water, acting by it- 

 self mechanically, exhibits in the course of time great 

 erosive results. The hardest rocks can not resist it, much 

 less the softer ones. The Pulpit Rock, so called, at Na- 

 hant, Mass., seen in Fig. 37, is an example of the erosive 





Fig. 37. 



action of the waves continually dashing against it year 

 after year. But little of the rock is worn ajvay each 



