THE BAHAMA ISLANDS 153 



the sands have been more or less cemented into a soft, porous rock. The form- 

 ation, then, is found varying from the loose, incoherent sands of the beaches and 

 sand dunes, to the older portions inland, composed of solid rock, fit for building 

 purposes. The weathering of this coralline rock is mostly a chemical process. 

 The rain water, with carbon dioxide in solution, dissolves out all the soluble 

 portions, carrying them off in solution, while the more insoluble matter is left 

 to form soil. This solubility, as with most limestones, is very great. It is 

 estimated that at least 100 feet of the rock must be weathered to leave 1 foot 

 of soil, and this without taking into account the forces of denudation. 



Denudation of the little soil formed has been rapid, so that the underlying 

 rock is exposed everywhere. The rock,, upon exposure to the weather, becomes 

 more or less indurated upon the surface, becoming so hard that when struck 

 it gives a metallic ring. The effect of weathering on the rock varies, depend- 

 ing upon its position. In the low-lying or nearly level places, where water 

 could stand, solution holes were started at the more soluble points, and the 

 result has been the formation of innumerable pockets, giving the surface a truly 

 honeycombed appearance. Most of these pockets are small, only a few inches 

 in diameter, and as a rule not exceeding 18 inches in depth, but larger holes 

 have been developed, either by solution or the falling in of the roofs of small 

 caverns. These are spoken of as " banana-holes," as .it is in these larger 

 openings that bananas are planted. 



The surface of the rock in these low grounds is ragged and very much 

 pitted, making traveling difficult, and interfering with the cultivation of crops. 

 Upon the hills and slopes, where the water drains off the surface readily, or 

 filters through the underlying rock, the result of weathering has been some- 

 what different from that in the lowlands. The surface has not been eroded into 

 pockets, but large, basin-shaped depressions have been formed, in which a black 

 loamy soil has collected. Much of the rock is exposed, and having a flat sur- 

 face, is spoken of as "plate rock," in distinction from that surface where 

 pockets occur, which is known as " honeycomb rock." It is partly upon these 

 surface characteristics that the different soils are popularly classified, and 

 partly, also, upon the coppice growth. 



SOIL TYPES. 



As the geological formation and physiographic features of all the Islands 

 are the same, a great diversity of soil types is not found. In all, seven types of 

 soil are recognized as follows: Coral Sands, Bahama Black Loam, Bahama 



