On the Gulf Stream and the Keys of Florida, 51 
But even if we admit the probability of such a condition of 
things, we do not get rid of the main difficulty; for in that case 
there is no apparent reason why the coral should not grow over 
the whole area at the same time, as an immense ‘coral forest, in- 
stead of in the form of successive reefs. In a word, the fact that 
the corals grew in the form of successive reefs, concentrically dis- 
sed from north to south, proves, as it seems to me, incontesti- 
bly, that the conditions necessary for coral growth have also been 
progressively formed in the same direction. The horizontal ex- 
tension of coral through so great a space proves also the progres- 
sive extension of necessary conditions; in other words, it proves 
that the sea bottom has been gradually rising from the north to- 
wards the south. ; 
uch a gradual rising of the sea bottom may be attributed to 
, viz:—first, gradi 
agency ; and second, filling up by sedimentary deposit. 
evidences of such igneous elevation upon the keys as we 
4pon the main land; but the more careful observations of Prof. 
Agassiz have satisfactorily explained these deceptive appearan- 
ces, so that we ma now say with confidence that there is not 
the slightest evidence of such elevation, but much evidence to 
of the reefs of "Florida, let us attempt to prove that such deposit 
has in fact taken place "ander the i uence of the Gulf Stream. 
It is a well known law of curren sediment, that if 
om 
of their sediment upon the bottom; but if, on the contrary, their 
Velocity ig ledbtuded they abrade their beds and banks. If, 
therefore, the velocity of a stream is greater on one side than on 
the other, abrasion will take place on the former, and deposit on 
the latter, Now, if such a stream, ng sediment, make a 
pee Si curve, the velocity will always be greater on the outer, 
and on the inner side of the sweep. Hence there must 
