214 



PHYSICAL GEOLOGY 



-H^ : 



The second was built in 1864, also about 700 feet from the shore, but this now stands 



on the edge of the water and has been abandoned for a new tower still further inland. 



A remarkable case of marine erosion is exemplified in an island in the North Sea, 



Helgoland, whose circumference has been reduced from 120 miles in the ninth century 



to 45 in the fourteenth, 8 miles 

 in the seventeenth, and to an 

 islet only 3 miles in circumfer- 

 ence at present. The remnant 

 has probably survived because 

 of its greater height (170 feet) 

 and because of the somewhat 

 more resistant character of the 

 rock (Figs. 202, 203). 



Sea-captured Streams. 

 — When streams on ap- 

 proaching the seashore 

 turn and run parallel to 

 it for some distance be- 

 fore entering it, they are 

 sometimes cut in two as 

 a result of the more rapid 

 erosion of the coast at 

 some one point (Fig. 204 

 A, B). Streams which 

 have been recently af- 

 fected in this way enter 

 the sea over falls. 



Raised Beaches. — 

 Shores that have been 

 raised (Fig. 205) are 

 sometimes marked by sea 

 cliffs, beaches (Fig. 206), 

 sand spits, and bars, un- 

 less the elevation took 

 place so long ago that 

 stream erosion and the 

 weather have destroyed 

 these. On the coast of 

 Scotland the beaches rise one above another to a height of 100 feet, 

 and the old sea caves are sometimes used as stables. The raised 

 beaches of Norway and Scotland are occupied by villages, and 

 without them the shores would often be deserted. On the coast of 



1'ic;. 204 A, B. — Block diagrams showing how 

 stream may be captured by marine erosion. 



