WATER SUPPLY OP EASTERN AND SOUTHERN FLORIDA. 129 
a heavy growth of hardwood trees. The soil consists of a rich 
humus due to the accumulation of leaves. Beneath the humus 
is usually found several feet of orange yellow sand. 
Sandy hammock lands : The sandy hammock lands as de¬ 
veloped in the sections bordering the coasts are of wind-blown 
sands or low dunes on which vegetation has gained a foothold. 
Various hardwood trees grow on this type of land. It has been 
found in many instances desirable for orange culture. It is used 
also to some extent in vegetable growing. The open nature of 
the soil, however, results in a heavy loss of fertilizer from 
leaching. 
Scrub : Scrub is a term applied to very sandy lands which 
support a dense growth of shrubby plants. The sandy pine 
lands often pass very abruptly and with no apparent reason into 
scrub. Few attempts have been made to utilize the scrub lands 
for farming purposes. 
Sand dunes : The sand dunes both of recent and of earlier 
formation occur frequently in Florida particularly along the 
coast. The sand dune soil has been found especially adapted to 
the growing of pineapples, the extensive pineapple farms of St. 
Lucie County being largely located on quiescent dunes. 
River swamp : The river swamp lands support a dense 
growth of hardwood trees. On the smaller streams where the 
elevation is sufficient to permit of successful drainage these lands 
if cleared would furnish desirable trucking and farming land. 
Salt marsh : Extensive salt marshes occur along the Atlantic 
coast and bordering the streams entering the ocean. 
UNDERGROUND WATER: GENERAL DISCUSSION. 
SOURCE. 
Rainfall : The chief source of underground water is the 
rainfall. Water vaporized through the energy of the sun passes 
into the atmosphere and is precipitated .over the land as rain or 
condensed as dew or fog. The vapor is supplied to the atmos¬ 
phere by evaporation, principally from the ocean, which, occu- 
