130 
FLORIDA STATE GEOLOGICAL SURVEY. 
pying three-fourths of the earth’s surface, is continuously ex¬ 
posed to the sun’s rays. To the vapor from the ocean is added 
that arising from inland waters, from the dry land surface to 
the earth, and from the leaves of plants. 
Small additions to the underground water supply may come 
through any one of a number of other possible sources, but the 
total amount thus added is relatively small and may be omitted 
in a general discussion.* 
ANNUAL RAINFALL. 
The annual rainfall is the measure of the column of water 
that would accumulate at any spot in the course of a year, if all 
that falls should be preserved. The measurement is commonly 
stated in inches. The average rainfall for the State as a whole 
for the fifteen years, from 1892 to 1906, inclusive, as deduced 
from the U. S. Weather Reports, was 53.17 inches, annually. 
The year 1907 was a year of less than average rainfall, 49.15 
inches, and if this year is included the average for the sixteen 
years, 1892 to 1907, falls below 53 inches, being 52.92 inches. 
If longer periods be considered the variation from this average 
is not sufficient to materially change the result. The area cov¬ 
ered by this report lies in that part of the State supplied with 
about the average rainfall, and 53 inches may be safely assumed 
as a close approximation to the annual rainfall for this section. 
DISPOSITION OF RAINFALL. 
Of the total rainfall of any area, (1) a part is returned as 
vapor to the atmosphere without having entered the earth; (2) a 
part is carried off by streams and rivers to the ocean without 
penetrating the earth; (3) a part is absorbed into the earth. 
..(1) WATER EVAPORATED WITHOUT ENTERING THE EARTH. 
Immediately following a rain the atmosphere is nearly or quite 
*A recent discussion of possible sources of underground water other 
than rainfall will be found in Bulletin 319 , U. S. Geol. Surv., by M. L. 
Fuller. 
