1 82 CORALS AND CORAL LSL.ANDS. 



opening toward the sea, or upon the surface of the Key. 

 Beyond the reach of ordinary tides, and of the waves raised 

 by moderate winds, the pot holes are generally lined with coat- 

 ings of solid, compact, and hard limestone, varying from a 

 thin layer to a deposit of several inches in thickness, and 

 following all the sinuosities of the cavities in which they are 

 accumulating. It is plain from their structure that these coat- 

 ings are a sub-aerial formation, increasing by the successive 

 accumulations of limestone particles left upon the older rock 

 by the evaporation of water thrown upon the Key when the 

 ocean is so violently agitated as to dash over the whole Key. 

 Frequently the hollow of these coated pot-holes is further filled 

 with consolidated oolite ; or thin layers of fine-grained oolite 

 alternate with a coat of compact limestone, throughout the 

 excavation, which often has been filled in this way up to the 

 general level of the surrounding surface. Occasionally these 

 regenerated surfaces are again hollowed out by the action of 

 storms, and the result is a dismantled pot-hole, in which their 

 structure and the mode of their filling is distinctly exhibited. 



" The stratification of the main mass of these Keys is very 

 peculiar. Though evidently the result of an accumulation of 

 oolites through the action of high waves, the beds are pretty 

 regular in themselves, but slant in every direction toward the 

 sea, showing that they were deposited under the action of 

 winds blowing at different times from every quarter. It is 

 further noteworthy, that, while the thicker layers consist of 

 oolitic grains distinguishable by the naked eye, there are at 

 intervals thin layers of very hard, compact limestone, alter- 

 nating with the oolitic beds, which have no doubt been formed 

 in the same manner as the coating of the pot-holes.'' 



The oolitic limestones, referred to by Prof. Agassiz as the 

 description states, are not the true coral reef-rock, the basement 

 rock of the reefs, but the superficial beach sand-rock and drift 

 sand-rock of the preceding pages, which are very generally 

 oolitic in structure. 



The Bei-muda or So7?iers' Islands. — The Bermudas are the 

 parts of a single atoll, as first announced by Major-General (then 



