CRUSTAL MOVEMENTS 



185 



holes bored by marine animals. It is inferred, therefore, that be- 

 tween the years 235 and 1749, the land on which the temple stood 

 sank until the water was 21 feet above the bottoms of the columns, 



Fig. 180. The submerged valley which is believed to be the continuation 

 of the Hudson Valley. The position of the valley is indicated by the 

 contours. (Data from C. and G. Survey.) 



and then rose again so that the floor of the temple was above sea- 

 level. 



These illustrations show that the land and sea change their 

 relations to each other. It is probable that this has been true since 

 lands and seas came into existence. It is not always possible to say 

 whether it is the land or the sea-level which has changed; but it 

 seems probable that the sea-level rises and falls from time to time, 

 and that the surface of the land also moves. 



Does the sea or the land change level? There are several 

 things which may make the sea-level rise or fall. 1 . If, for example, 

 the bottom of the sea-basin were to sink, the surface of the sea 

 would be made lower. 2. Again, the gravel, sand, and mud washed 

 down from the land to the sea and deposited in its basiri~must make 



