AGASSIZ: BAHAMAS. 13 



Substituting older limestones in place of the oceanic deposits which 

 Darwin imagines to have been made on the shores of the West Indian 

 sea, and it seems to me that he has himself in his account of the coral 

 reefs of the West Indies, the substance of which I have quoted above, 

 given an admirable summary of the possible condition of the substruc- 

 ture of coral reefs in areas where it did not appear that his theory fur- 

 nished a satisfactory explanation of the facts. 



The following report must decide how far the explanation given by me 

 satisfies the conditions of the coral reefs existing in Cuba, the Bahamas, 

 Florida, the Bermudas, and other West Indian areas. 



The plateau upon which the Bahama Islands are situated is connected 

 with the shore plateau (the " Blake Plateau ") of the east coast of the 

 United States, extending in a triangular shape from Cape Hatteras to 

 the Little Bahama Bank. 1 Its western face is separated by compara- 

 tively shallow straits from Florida ; these become deeper as we proceed 

 south, and their depth increases regularly towards the westward to the 

 deepest points between Cape San Antonio and Yucatan. 



The Bahama Plateau is separated from Cuba by the Old Bahama 

 Channel. It gradually increases in depth eastward as we go from 

 three hundred fathoms off Cay Frances to its greatest depth, over one 

 thousand fathoms, off Diamond Point, between it and Boca Guajaba. 

 (Plates I. and VIII.) The plateau itself slopes to the eastward at its 

 northern termination, as is well shown also from the line of soundings 

 to the north of the Little Bahama Bank parallel with it, and along the 

 axis of the Xorthwest Providence Channel separating it from the Great 

 Bahama Bank. 



The relations of the banks to the eastward of the Great Bahama Bank 

 are best seen from an examination of the hydrographic sections on Plates 

 IV. and Y., and of the charts, Plates I. and VIII. 



In attempting to explain the formation of the Straits of Florida, we 

 should remember that, in addition to whatever part the Gulf Stream 

 may have played in cutting them out, on the Florida 2 side of the straits 

 the land was nearly stationary during the time of the formation of the 

 Florida reefs, while on the Cuban side the coral reefs have been elevated, 

 and on the Bahamas the reefs now flourishing are in a region where there 

 has been considerable subsidence, increasing as we pass eastward. If 

 these movements of the Bahama Banks and of the laud on their sides 



1 See charts, Figures 56 and 176, " Three Cruises of the Blake " 



2 See Suess, Antlitz der Erde, Vols. I. and II., Chapters X. and XVII. 



