THE WEST INDIAN WATERS 13 



temperature is equable, normally between 70 and 80 

 at sea-level, and varying above or below this only in lim- 

 ited localities where land barriers cut off the winds, or 

 upon the mountain summits. Were it not for the humid- 

 ity of the atmosphere, the general temperature of the 

 islands would be most enjoyable. 



Another feature of the American Mediterranean is its 

 wonderful submarine topography. This is so intimately 

 connected with the topography of the land that the rela- 

 tions of the latter cannot be understood without a brief 

 description of it. Beneath the blue waters is a configura- 

 tion which, if it could be seen, would be as picturesque in 

 relief as the Alps or Himalayas. Nowhere can such con- 

 trasts of relief be found within short distances. Some 

 deeps vie in profundity with the altitudes of the near-by 

 Andes, so that between the great Brownson Deep of 

 twenty-five thousand feet to the summit of Chimborazo 

 there is a difference in altitude of nearly ten miles. 



The deepest cavity yet revealed in the Atlantic occurs 

 at a point due north of Porto Rico, where the soundings 

 record a depth of forty-five hundred fathoms. This is 

 known as the Brownson Deep. Some of the depressions, 

 like the Bartlett Deep, are narrow troughs, only a few 

 miles in width, but hundreds of miles in length, three miles 

 in depth, and bordered by steep precipices and escarpments. 

 Others, like the Sigsbee Deep, in the Gulf of Mexico, 1 are 

 great circular basins. There are long ridges beneath the 

 waters, which, if elevated, would stand up like islands of 

 to-day, and, as has been shown, have an intimate relation 

 to the mountains of the land. Again, vast areas are un- 

 derlain by shallow banks less than five hundred feet deep 

 and often approaching the surface of the water, like that ex- 

 tending from Jamaica to Honduras and the Bahama banks. 

 The greater islands and the mainlands are bordered in 

 places by submerged shelves. 



1 These three deeps, named after naval commanders of to-day, were bestowed 

 by Agassiz in commemoration of the part which they took in surveying them. 



