OCKLOCKNEE AND AUCILLA RIVERS. 117 
irregularities no doubt existed, but certainly no such pronounced 
basins and hills as those which are found at the present time. The 
striking features in the topography we must assume have developed 
■since the area became dry land, and subjected to the modifying influ¬ 
ences of eroding agencies in contrast to depositional agencies, which 
chiefly influence submerged areas. The topography, as it is seen in 
this region to-day, including the hills, valleys and many lake basins, 
which add so much to the beauty of the landscape, has resulted, we 
may believe, from natural agencies acting through a long period of 
time and still operating. The topographic and physiographic devel¬ 
opment is, therefore, a part of the geologic history and includes 
chiefly the history of the region after it became dry land. 
The topographic forms which result from erosion and disinte¬ 
gration of the land surface vary in character in keeping with the 
variations in the intensity of action of the different eroding agencies, 
and also in accordance with variations in the formations which are 
subjected to these influences. It thus follows that eroding agencies 
are by no means of the same intensity the world over. A warm, 
moist climate, accompanied by dense vegetable growth, affords 
unusually favorable opportunity for those disintegrating processes 
that are promoted by the presence of organic acids and carbon 
dioxide gas. An analagous variation in intensity of action charac¬ 
terizes many of the other agencies of disintegration according to the 
varying conditions under which they operate. Moreover, succes¬ 
sive formations are by no means uniform in composition or in resist¬ 
ance to agencies of decay. To understand the resulting land forms 
it becomes necessary, therefore, to take into consideration both the 
character of the formations and the conditions under which the 
disintegrating agencies have operated. While the land forms 
usually result from a combined action of many agencies, yet the 
predominating influence of a single agency, or a group of agencies, 
may often be.recognized. 
The preceding pages contain a description of the formations 
undertying this area, and also a brief account of climate and vegeta¬ 
tion. Calcareous formations are present either at the surface or 
underlying other deposits. Over a considerable part of the area 
these rocks are occasionally exposed, and it is only in the south¬ 
western part of the area that they are so deeply buried as not to 
affect the topography. The rainfall is heavy; much of the 
drainage is subterranean; the. native vegetation is for the most part 
8 
