152 SOILS AND AGEICULTDKAL CONDITIONS 



away much of the light soils on the higher elevations. Heavy dews are 

 common during the winter, and do much towards keeping up plant growth 

 during the droughts. Cool winds from the northeast are common during the 

 winter, and in August, September and October, destructive hurricanes may be 

 expected. The prevailing winds are those of the " trades," which are generally 

 easterly, varying to northeasterly and southeasterly. The Islands are so nar- 

 row that these winds greatly modify the climatic conditions. On account of 

 their equable climate the Islands are growing in popularity as a winter resort. 



GEOLOGY.' 



In their physiographic and geological features the Bahamas do not differ 

 materially from one another. The topography consists in general of a range 

 or series of ranges of low hills running lengthwise of the islands, with low in- 

 termediate valleys. The hills rise to elevations rarely exceeding 250 feet, 

 and on the windward or northeastern side, which is commonly known as the 

 " north shore," they consist of rounded dunes of loose, incoherent sand. In- 

 land they become somewhat higher, are more stony and rugged, and often end 

 on the leeward coast as low bluffs or promontories. 



The valleys are but slightly elevated above sea-level, and the lower portions 

 are often- occupied by brackish ponds or lakes, the waters in many of which 

 rise and fall with the tides, as they have siibterranean connections with the . 

 sea. These valleys contain no running streams of fresh water, and surface 

 drainage systems have not been established on any of the islands, with the 

 exception of Andros. Even on this island the streams are few and small. 

 The valleys, then, are not solution valleys, such as are found in limestone 

 countries, but are original depressions between the ranges of hills or sand dunes. 

 The drainage is therefore through the porous underlying rock, and through 

 numerous fissures and crevices into the subterranean caverns, and thence 

 through openings into the sea. 



Along much of the windward shore, and in the bights on the leeward 

 shore, occur beaches or narrow beach plains of sand, elevated a few feet above 

 high water level, and varying in width from only a few yards to as much as 

 half a mile. 



The rock formation consists of shell and coral sand more or less solidified, 

 to a limestone. By wave action the coral and shells have been pulverized and 

 cast up on the beaches, where they have been picked up by the winds and 

 blown inland, forming sand dunes. Later by infiltration of carbonate of lime. 



