CORAL LIMESTONE. 



rock into quadrangular blocks of from one to two 

 feet in the side. As far as external appearance 

 and character went, it might have been taken for 

 any old roughly stratified rock. As to position, the 

 strike of the rock was parallel to the direction of 

 the long diameter of the island and reef, or east and 

 west ; and it dipped on the north and south sides 

 of the island to the north and south respectively, or 

 from the island towards the reef at an angle of 8° or 

 10°. At the east end of the island it was not visi- 

 ble, but at the west it appeared from under the sand 

 in two places, in one being horizontal, and in the 

 other having a slight flexure cr anticlinal line, 

 which ranged also east and west. The rock was in 

 many places much worn by the wash of the break- 

 ers, which had also a good deal undermined it in 

 some places, and many blocks had fallen down in a 

 line. The joints were parallel to the dip and strike 

 respectively. The rise and fall of tide here was 

 fourteen or fifteen feet, and at high water the 

 upper part of the rock was just about covered ; at 

 low water the reef was dry for a small space all 

 round the island. Now the question is, how or 

 under what circumstances did the loose calcareous 

 sand and fragments become hardened into solid 

 stone, acquire a regular bedding and a jointed 

 structure, and the planes of stratification assume an 

 inclination of 8° or 10°. If it be supposed that a 

 regular deposition on a slope ot 8° took place every 

 high tide, and a gradual and successive induration 



