7 8 FLORIDA GEOLOGICAL SURVEY—FOURTH ANNUAL REPORT. 
The basin of Lake Okeechobee represents probably a natural de¬ 
pression which existed at the time of the uplift. According to the 
sounding made by Wright, this basin, now a lake, has an average 
depth of about 12 feet, and a maximum depth of 22 feet. When first 
elevated such basins contain salt water which subsequently becomes 
fresh by the influx of water from the surrounding drainage basin. 
The unusually level character of the country, the heavy rainfall, 
and the overflow from Lake Okeechobee have resulted in the forma¬ 
tion of the marshy conditions and the accumulation of the muck 
deposits which now characterize the Everglades. The process has 
been a slow accumulation of muck which is now found to a depth of 
5 to 12 feet, depending upon the natural irregularities of the sur¬ 
face. The length of time involved in the accumulation of this muck 
is difficult to estimate. A crude measure of the time that has 
elapsed since the earth movements that brought this part of the 
State above sea level and originated the conditions which produced 
the Everglades is found in the amount of cutting that has been done 
by the several streams draining from the ’Glades. The Miami River 
has cut back from the coast, partly by mechanical wear and partly 
by solution, a distance of about six miles. The waterfall at the head 
of this river has now been cut out by the dredging operations. The 
other streams have cut channels proportionate to the volume of 
water modified by the character and hardness of the formations 
through which they are cutting. 
An extensive plan for the drainage of the Everglades has been 
made and is being carried out under the direction of the Drainage 
Commission of the State. Aside from the Everglades, many smaller 
tracts of muck, prairie, and other wet lands in Florida are being 
drained, either by private enterprise or by communities under spe 
cial legislative act providing for drainage districts. 
ALLUVIAL LANDS. 
The alluvial lands of Florida have been but little used for agri 
culture. Many of the streams and rivers have flat bottomed valleys 
densely wooded with hardwood trees. Within these valleys the 
streams are often confined to no definite channel. During the sum¬ 
mer, owing to the heavy rains, together with the impeded flow 
through the trees, the valleys are as a rule flooded. In many of 
these the streams could be confined to a central channel and a con¬ 
siderable part of the valley made available for agricultural purposes 
by clearing out the dense growth of trees. However, the expense of 
