1897-9^]- HIGH PLATEAU AND SUBMARINE ANTILLEAN VALLEYS. 367 



The valleys beneath the Antillean seas have, in part, been excavated 

 out of disturbed strata, as is suggested by the exposures of the 

 formations on the adjacent islands, and also in part out of undisturbed 

 beds, which last occurrence is generally the case on the coastal plains 

 of the continent. The formations immediately adjacent to the drowned 

 valleys belong everywhere to late geological periods. 



The characters of the submarine valleys — in their magnitude ; in 

 their declivity ; in their being extensions of existing rivers ; in their 

 receiving tributaries from various directions, like modern streams ; 

 and in the long reaches of their floors, with low gradients, resembling 

 gradation plains and base levels of land valleys — are so strongly 

 analogous to land features, as to more than indicate their common 

 origin. Indeed, the likeness is so strong as to suggest a satisfactory 

 explanation of the submarine valleys off the south-eastern coast of 

 North America, and those of the West Indies, that is to say, they 

 appear to be drowned valleys of atmospheric origin. With the occur- 

 rence of the submerged valleys thus explained, it follows as a con- 

 clusion that the West Indian region and the margin of the continent 

 stood once nearly as high as the drowned valleys are traceable, which 

 feature extends nearly to the floors of the Antillean basins. This 

 implies a late elevation of the region to a height of two or three miles, 

 which altitude is greater than that generally assumed in late geological 

 times. But the recent extraordinary depression of the Antillean plateau 

 does not extend to the western boundary of the region. Between the 

 east and the west there was a zone of diminished terrestrial movements- 

 The broad valley which is now the floor of the Gulf of Mexico, has 

 its counterpart setting into the continent from the Pacific side, but 

 the Mexican barrier between the two oceans has only been recently 

 elevated — in part to 8,000 or 10,000 feet. This seems then to be a 

 physical compensation for the sinking of the Antillean plateau of the 

 east, and illustrates stupendous movements in the opposite direction, in 

 late geological times. 



Many writers have regarded the West Indian Islands as remnants of 

 mountain ranges submerged, but no standard was found for measuring 

 the amount of depression, until the application of geomorphy to the 

 drowned valleys was suggested by the writer. It might have been 

 formerly supposed that the West Indian basin alone sank, while there 

 was no considerable change of continental elevation ; but such a hypo- 

 thesis is now opposed by the analysis of the character of the valleys. 

 Nor have ocean currents greatly deepened the channels, for even the 



