Br. J. W. Sjjencer — The AntiUean Continent. 449 



accumulating evidence of great systems of submerged valleys, or 

 fjords extending from the commonly buried lower reaches of all 

 the great rivers, upon the terrestrial deformation involved in the 

 changes of level over large regions and upon the distribution of 

 the characteristic forms of life. The present investigations confirm 

 and amplify the history of the coastal plain of the northern 

 continent. 



The forms of the valleys of the southern Appalachian mountains 

 and of the coastal plain were illustrated, showing that their charac- 

 teristics are mostly due to the insidious action of rains and rills, 

 producing different results according to the slope or elevation of 

 the base-level of erosion. This study was introduced in order 

 to compare the drowned canons witli the land valleys. 



The gentle but varying amount of epeirogenic deformation has 

 permitted of correlations which would have been prevented had 

 the sharp erogenic disturbances of recent times prevailed over very 

 wide areas. 



The submarine valleys or fjords have been correlated into systems 

 with their tributaries, and in all cases they connect with the partly 

 buried land valleys. The continent is bordered by a sub-coastal 

 plain from 100 to 300 miles wide, which is characterized by plateaux 

 or terraces now submei'ged to even 3000 or 5000 feet, with the 

 oceanic bed beyond depressed to 12,000 feet or more. Crossing 

 these plateaux, the cafions reach to depths of thousands of feet, and 

 terminate in embayments into margins of the continental shelves. 

 The Gulf Stream occupies portions of three distinct valleys, exclusive 

 of its tributaries, which have been only slightly modified on the 

 cols between them. The drainage of the West Indian continent 

 was almost entirely to the west, there being only two or three long 

 valleys upon the eastern side of the Windward mass. The fjords 

 reach to the bottoms of the Gulf of Mexico and Carribean Sea, 

 whose beds are shown to have been recent land plains (except the 

 Sea of Honduras, in part). The valleys of the existing rivers, 

 often deeply buried near their mouths, are in magnitude proportional 

 to their fjords beyond. 



The analogy between the land valleys and the drowned canons 

 is so complete that the unqualified conclusion is reached that the 

 fjords are evidences of atmospheric erosion to their depths (with 

 perhaps one or two exceptions), or in other words there was an 

 elevation of the region, as high as the fjords are deep, less the 

 reduction by differential deformation, which is more or less 

 determinable. Thus it appears that there has been a post-erosion 

 subsidence to an amount from 8,000 to 12,000 feet, carrying down 

 the Antillean plains to form the present sea-basins, and the high 

 lands to form the islands. 



The general Miocene depression of the whole region left only 

 small islands, and during this submergence portions of the region 

 appear to have sunk to abyssmal depths. 



The Pliocene period was characterized by the connection of the 

 two Americas by way of the West Indian bridge, part of which 



DECADE IV. VOL. I. — NO. X. 29 



