WEST INDIES. 
2G9 
coral-rock, some of them being about a hundred feet in 
height, is easily explained by the elevatk n of banks fringed 
on their windward sides by coral-reefs. On this view, how- 
ever, we must suppose either that the great Bahama sand- 
banks w r ere all originally deeply submerged, and were 
brought up to their present level by the same elevatory 
action which formed the linear islands ; or that during the 
elevation of the banks, the superficial currents and swell 
of the waves w T ore them down, and kept them at a nearly 
uniform level. But this level is not quite uniform ; for in 
proceeding from the N. W. end of the Bahama group towards 
the S.E., the depth of the banks increases, and the area of 
land decreases, in a very gradual and remarkable manner. 
The view that these banks have been worn down by the 
currents and waves of the sea during their elevation, seems 
to me the most probable one. This view is also, I believe, 
applicable to many of the submerged banks, in widely dis- 
tant parts of the West Indian sea ; for, on any other view, 
the elevatory forces must have acted with astonishing uni- 
formity. 
The shore of the Gulf of Mexico, for a space of many 
hundred miles, is formed by a chain of lagoons, from 1 to 20 
miles in breadth (Columbian Navigator, p. 178, &c.), con- 
taining either fresh or salt water, and separated from the 
sea by linear strips of sand. The shores of southern Brazil, 
and of the United States from Long Island (as observed by 
Professor Bogers,) to Florida, have the same character. 
Professor Bogers, in his report to the British Association 
(vol. iii. p. 13), speculates on the origin of these low, sandy, 
linear islets ; he states that the layers of which they are 
composed are too homogeneous, and contain too large a 
proportion of shells, to permit the common supposition of 
their formation being simply due to matter thrown up, 
■where it now lies, by the surf : he considers these islands 
as upheaved bars or shoals, which were deposited in lines 
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