I30 FLORIDA GEOLOGICAL SURVEY-NINTH ANNUAL REPORT. 
spring heads is more rapid to the northwest or up the dip, which 
thus accounts for the greater length of the tributary streams on the 
northwest side of the main streams. It is owing to these conditions 
that tributaries of the St. Marks and Wakulla Rivers reach to within 
a mile or so of the Ocklocknee River, while tributaries of the Ock- 
locknee in turn reach to within a few miles of the. Apalachicola 
farther to the west. The drainage divide of the Ocklocknee on the 
east side is for the most part within one mile or so of the stream. 
Another feature closely related to that just mentioned is the 
fact that as a rule the land lying directly to the east of each main 
stream is higher than that of the west, or the rise to high land on the 
east side is more abrupt than on the west or northwest side. Thus 
the slope to the Ocklocknee River in Gadsden County is as a rule 
very gradual, while 011 the east side of the river the rise to high or 
relatively high land is much more abrupt. This applies also, 
although possibly not in quite so marked a degree, to the Aucilla 
River, and is very pronounced for the Apalachicola River. This 
feature of the stream development is possibly accounted for by tbe 
fact that the prevailing dip is to the south or southeast, while the 
course of the stream is southwest. Under these conditions the 
streams tend to shift to the southeast. Also from the fact that 
there are. few mostly small tributaries from the east side, it follows 
that the land surface to the east is much more slowly reduced in ele¬ 
vation by surface wash than is that on the west side. The sugges¬ 
tion that these streams with high lands to the e.ast may lie in faults 
naturally presents itself. In the structure, however, presence of 
faults has not been found, and there seems to exist scarcely more 
than obscure indications of minor possible interruptions in the dip. 
TOPOGRAPHIC FEATURES. 
Another feature that can not fail to attract attention is the very 
pronounced differences in the. topography directly east and that 
west of the Ocklocknee River. East of the river in Leon County 
are found many lakes and lake basins and topographic details con¬ 
trolled by solution, while the drainage is chiefly by underground 
streams. West of the river, on the other hand, lakes and lake 
basins are wanting and drainage is by surface streams. The 
plateau level west of the Ocklocknee is about 250 feet above sea. 
East of the river the maximum elevation is probably about 240 feet, 
a difference that can not. of itself account for the pronounced differ- 
