202 E. B. Hunt on the Florida Reef. 
fathom curves around the west end of the Bank, is unmistake- 
ably a special formation subsequent to the general shaping of 
the Gulf bed. The actual causes now at work in producing 
coral and shell material, and in grinding and transporting 1t, 
must necessarily result in a building up from the bottom along 
the line of the eddy current to the westward. 
ombine with this the fact that the most effective winds and ~ 
waves, both of trade and hurricane origin, come in upon the 
reef from the S.E., and must therefore help to transport detri- 
tus to the westward and northwest. Moreover, the heavy waves 
which wear the front face of the reef must work some of the 
nent at Key West. Fort Jefferson, resting wholly on sand 
foundations, has settled in all its cireuit, and in some portions 
it has gone down nearly a foot, showing that a deep sand bed 
has yielded thus much to compression. : 
In the sheltered waters among these keys, there is an active 
growth of branching corals, &e., on Be foundations, whieh are 
torn up by storms and tossed on the beaches by the waves, 
such an extent as to afford the vast mass of concrete materials 
used in the masonry of Fort Jefferson. There are however 10 
_extended rock masses, and the great vitality of the ooralé 
shown in an active renewal of growth on dead coral sprigs . 
is my impression that the mass of materials forming Tortug! 
keys and banks has been transported westward by the dy 
current, and north and northwest by the south and soutbense 
stor urricane waves, from the reef abreast and east ° 
Marquesas. The shaping of the bottom indicates this, and it * 
