ANOTHER POSSIBLE CAUSE OF THE GLACIAL EPOCH. 143 



which they enter through channels so deep that, if ele- 

 A^ated into land, they would resemble the great canons of 

 Western America. Some of the channels which cross the 

 Blake Plateau are traceable for 200 to 300 miles, and reach 

 depths of 10,000 feet before being lost in the suboceanic 

 embayments. Similar features are presented by the deep 

 channels which furrow the shelf of the Bahama Islands, and 

 also by those of the Gulf of Mexico. But there is one 

 remarkable featiu'e which ought not to be omitted from 

 notice here, viz., that the submerged channel between the 

 peninsula of Florida and the Bahamas appears to have been 

 a saddle or watershed, from which canons descended east- 

 wards towards the Atlantic, and westwards towards the Gulf 

 of Mexico. Professor Spencer has named the latter the 

 " Floridian " Valley. The Mississippi and all the great rivers 

 which enter the northern shore of the Gulf of Mexico have 

 their apparent prolongations in well-defined submerged 

 river-valleys, to which Professor Spencer has given definite 

 names. They have their final " embayments " at depths of 

 about 9,000 to 10,000 feet. The same is also true of the 

 rivers entering the Atlantic. The submarine canons are in 

 effect drowned river extensions opening out on the abyssal 

 floor at depths of about 10,000 feet, under the surface of 

 the Gulf Stream. Amongst the West India Islands the 

 " Haitian " canon passes on to the Atlantic floor between the 

 Bahama Banks and the islands of Cuba and Saint Domingo ; 

 other examples might be cited, but enough has been said to 

 give a general idea of the author's deterixiinations. It is now 

 time to state the conclusions at which he arrives. He main- 

 tains that the physical features determined by the soundings 

 are such as can only be explained by supposing an uplift of 

 the whole region bordering the Atlantic to the extent of the 

 depth of these submerged river channels, namely, 10,000 to 

 12,000 feet as compared with the present sea-level, by which 

 the coast of South America was connected with that of the 

 Northern Continent by a plateau of continuous land now 

 constituting the floors of the West India Islands, and 

 converting them into the " Antillean Continent." This 

 uprise gradually lessened westwards, and was counter- 

 balanced by a depression of Central America, owing to 

 which the Gulf of Mexico and Caribbean Sea were connected, 

 with the Pacific. From geological considerations this uprise 

 took place at two epochs, viz., the PHocene and Pleistocene, 

 with an intervening epoch of depression ; and the later uplift 



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