210 CORALS AND CORAL ISLANDS. 
Region between the Florida Reefs and Cuba.— Through 
the labors of Pourtalés, in connection with the soundings 
by the Coast Survey, interesting facts have been brought to 
light respecting the sea between the Florida reefs and the 
opposite shores or reefs along Cuba and the Bahamas (see 
Plate XI.). A few paragraphs on the region, by Pourtalés, 
are cited from his memoir.t 
“Tn transverse sections of the channel the greatest depth 
is nearest its southern or eastern shore, and in a longitudinal 
section the depth diminishes in passing toward the north, 
finding its minimum in the narrowest part between Cape 
Florida and the Bemini Islands, after which it increases 
again. In a transverse section between Key West and 
Havana, the greatest depth is 855 fathoms; between Som- 
brero Light and Elbow or Double-Headed Shot Key on the 
Cay Sal, or Salt Key Bank, 500 fathoms; between Carys- 
fort reef and Orange Key on the Great Bahama Bank, 475 
fathoms; and between Cape Florida and the Bemini Islands, 
370 fathoms.” 
Pourtalés says of the bottom outside of the Florida reefs : 
“‘ Although the deep blue color of the water after passing 
the reef seems to indicate a very abrupt slope, there is in no 
part of it anything to compare with the sudden deepening on 
the edge of the coral reefs of the Pacific Ocean, or even of 
the Bahamas or the coast of Cuba. The distance from the 
reef to the 100-fathom line is not less than three miles, and 
often as much as six. In this space the bottom consists of 
calcareous mud, and is not particularly rich in animal life. 
From ninety or a hundred fathoms to two hundred and fifty 
or three hundred, the bottom slopes rather gently in the 
1 Museum of Comparative Zodlogy, Illustrated Catalogue, Cambridge, Mass., 
1871. 
