SECOND ANNUAL REPORT—SOUTHERN EEORIDA. 
179 
tion that could not or would not have been collected before the advance 
of the railroad along the coast and across the keys, it is natural that 
some of the conclusions expressed may controvert those of writers who 
had to rely on more limited observations and had no way of knowing 
what was beneath the surface. Having lived for months on one of 
the keys and having seen some of the mainland the writer appreciates 
the disadvantages those who wished to get trustworthy data had to 
meet and overcome. In the preparation of this report he has aimed 
to give an easily understood account of the topography and geology of 
a fascinating region now easily accessible, and to indicate the bearing 
of the more striking features of the accumulated evidence on some 
geologic problems of importance. He has tried to present the more 
essential facts as briefly as is consistent with clearness. Hence he 
has given detailed evidence but seldom and has not discussed subjects 
that do not bear directly on the theme of his narrative. In particular 
he has not presented item by item the testimony for .or against his 
conclusions on minor points. A number of interesting problems he has 
barely mentioned. These he hopes to discuss in detail elsewhere. 
TOPOGRAPHY. 
GENERAL FEATURES. 
In a general review of the salient features of the topography of 
southern Florida, it is convenient to consider the mainland and the 
keys separately because on the mainland one can distinguish certain 
distinctly marked topographic units. Also, the features of the shore 
line may be taken up independently of the discussion of the varying 
forms of the land surface; for this reason the shore line topography 
is considered by itself, and as the subject is one of considerable inter¬ 
est on which little has been written, it is discussed briefly. 
Taken as a whole the topography of the Florida mainland has all 
the aspects of infancy. Drainage is defective, sloughs, shallow ponds 
and lakes abound. Most of the interior is a swamp, there are no well 
defined river systems nor stream valleys, and some of the short rivers 
that flow from the Everglades into the Atlantic are, where bed rock 
comes a few feet above tide level, characterized by rapids in their 
upper courses. 
This infantile aspect is due to two causes, one the actual recency 
of deposition of the beds, consolidated and unconsolidated, that consti¬ 
tute the land surface, and the other the slight elevation of the beds 
above tide level since deposition. The rocks have had relatively little 
time to decay, and there has not been an elevation of the land sufficient 
