OBJECTIONS TO THE THEORY OF SUBSIDENCE. 285 
porting nearly all the debris over the emerging reef and into 
the inner channels or lagoons; little is carried off and dropped 
in the deeper waters outside. The condition is like that on 
other coasts which the sea is extending. But there is this 
difference that the corals, the chief source of the debris, have 
a hold on the bottom because attached species, and the cal- 
careous sands are easily cemented; so that the reef they 
make becomes a solid bank. And further, the waves and 
tidal waters have this great area of reef and inner channels 
to receive the sands they distribute. Little debris reaches 
the outer slopes; and the most of this little finds lodgment 
among the corals within coral-growing depths. 
The Florida reefs well illustrate the facts. Off the great 
emerged banks there is, first, the region of growing corals, 
called the “ Florida reefs,” half a mile to a mile wide, and 
one to nine fathoms deep, where some spots of reef reach the 
surface ; and outside of this, on the south, there is the Pour- 
talés plateau at depths down to two hundred and fifty fath- 
oms, growing pelagic species. There is no talus. Some 
debris drops over the plateau; yet, as Mr. Agassiz’s figure 
shows, the amount is very small. The Florida Bank gets 
nearly all, and thus it has derived its height and extent. 
d. The view which Mr. Agassiz sustains that the Florida 
corals grew out on a basement made by pelagic growth or on 
the inner part of the Pourtalés plateau, and thus extended 
the great bank, has more to sustain it than the talus-theory. 
With only the facts that are open to view in the Florida seas 
no other explanation would be thought of. But there is one 
difference between banks over such a bottom and those in- 
creasing through a subsidence. With the former, the slope 
of the bottom would usually be gentle. While the explana- 
tion may answer as well as the subsidence-theory for the 
