182 
FLORIDA STATR GE^ROGICAT SURVEY. 
is no pinelanc! south of postmans River. Along the north line of Mon¬ 
roe County the pines grow in more or less disconnected areas separated 
by narrow and broad strips of cypress. In the vicinity of Naples the 
pines grow to the shore of the gulf; between Cape Romano and the 
mouth of Lostmans River they lie from ten to fifteen miles back of the 
outer face of a network of keys that constitutes the apparent shore 
line. 
As the trees grow on areas of quite different topographic aspect, the 
pineland of southern Florida may be divided according to the char¬ 
acter of its relief into dunes, rolling sand plains, rock ridges and flat 
lands. 
DUNES. 
That there may be no misunderstanding as to the sense in which the 
word is used, a dune is here defined as a heap of wind-moved sand. In 
other words it is a purely aeolian accumulation of material, and is thus 
distinct from deposits of sand that owe their relief, wholly or in part, 
to the action of water, whether this action has been that of currents 
or of waves. Hence dunes are sharply differentiated from beach 
ridges, those coastal accumulations of sand and other loose material in 
the shaping of which waves and wind-driven spray took part. Thus 
the ridge facing the ocean at Palm Beach is not considered a typical 
dune. 
In southern Florida the dunes lie near the coast. East of the Ever¬ 
glades and Lake Okeechobee they reach south to New River as a dis¬ 
continuous series of irregularly distributed mounds and ridges, some¬ 
times separated by considerable intervals of flat or gently rolling coun¬ 
try, or by stretches of shallow water yet seldom reaching more than a 
few miles inland and but rarely facing the open ocean. South of New 
River there are, so far as the writer knows, no true dunes. There are 
certainly none on the long chain of keys that extend from Biscayne 
Bay to the Marquesas. The nearest approach to dunes to be found 
along that 150 mile stretch of islands are the low indistinct ridges and 
mounds nowhere eight feet above mean sea level, that are more pro¬ 
nounced along stretches of beach facing breaks in the living coral reef, 
particularly where the water near shore has more than average depth 
or rather where the seaward slope of the bottom is greatest. These 
low heaps of sand from their position may be the work of the waves 
quite as much as the wind, in fact most, if not all, are true beach 
ridges. Their outlines may possibly be modified slightly by the drift 
of wind-borne sand but their main features are clearly due to wave 
action, particularly to the waves that break on the exposed beaches 
during a hurricane when tides four feet or more above mean high 
water mark facilitate the formation of in-shore waves much higher 
