THE WEST INDIAN BRIDGE. 19 



depths from twenty-five hundred to thirty-five hundred feet. From 

 its margin the edge of the continent drops abruptly to depths of 

 twelve thousand feet or more. On the western side of Florida the 

 drowned plains gradually slope down to about three hundred feet, 

 beyond which there is an abrupt descent to the abyss of the Gulf of 

 Mexico. The Yucatan plains extend as broad submerged banks to 

 about three hundred feet beneath the sea, and the sea floor then falls 

 rapidly to that of the Gulf of Mexico, at twelve thousand feet. Such 

 slightly submerged plains of great breadth occur on the banks be- 

 tween Honduras and Jamaica. The Windward Islands are frag- 

 ments of a plateau which an emergence of less than three thousand 

 feet would unite into one body of land. Both to the east and west of 

 Jamaica there are plateaus depressed to between three thousand and 

 four thousand feet. Still lower plateaus are indicated in the Carib- 

 bean Sea, which reaches to a depth of fifteen thousand feet. 



From the existence of these submerged plateaus it becomes 

 apparent that a change of elevation of from two thousand to four 

 thousand feet would not merely unite Cuba and Florida, but would 

 greatly enlarge the West Indian lands, and almost connect ISTorth 

 and South America. Such a change of elevation would nearly bar- 

 ricade the Antillean water into three basins — the Caribbean Sea, 

 the Sea of Honduras, and the Gulf of Mexico. The Sea of Hon- 

 duras, between Cuba and Jamaica, reaches to the phenomenal depth 

 of twenty thousand feet, in the form of a long, narrow channel. 

 The structure of these sea basins, at various depths, has been mapped 

 by many writers, but the character of the channels which dissect 

 the drowned plateaus had been almost entirely passed over until the 

 appearance of the writer's previous papers.* 



The Drowned Valleys or Fiords. — The greater number of 

 the submerged valleys discovered are found to be continuations of 

 buried channels of modern rivers. In some cases the valleys have 

 been so completely submerged that even the divides between those 

 trending in opposite directions have also been drowned — as, for ex- 

 ample, the straits of Florida. These drowned valleys have been 

 traced across the submarine plateaus and terminate in enlarged em- 

 bayments indenting the margin of the continental mass. A few 

 great submarine valleys are found parallel with the mountain 

 ranges. The continuation of many land valleys beneath the sea, 

 and others completely submerged, is shown in the accompanying 

 map (Plate III), and attention may now be called to a few notable 

 examples. 



* Terrestrial Submergence Southeast of the American Continent. Bulletin of the Geo- 

 logical Society of America, vol. v, pp. 19-22, 1893. Reconstruction of the Antillean Con- 

 tinent. Ibid., vol. vi, pp. 103-140, 1894. 



