MINERAL INDUSTRIES. 
33 
sively along- the Caloosahatchee River. Tampa Bay affords a com¬ 
pact limestone which often carries much silica. The Chattahoochee 
series of compact limestones occurs extensively in parts of West 
Florida. The marls are usually of local occurrence and are re¬ 
stricted to no part of the State. Shells, thanks to oyster industry 
of the present, and to the shell mound builders of the past, occur 
in inexhaustible quantities. 
The term “marl” in connection with road making is applied 
to any calcareous material that is sufficiently soft to admit of direct 
application to roads without previous crushing. The marls as a 
rule are taken direct from the pits to the roads. * With the soft 
marls, traffic over the road serves to crush, smooth, and pack the 
material, although the harder marls after being spread on the road 
are broken up by hand or crushed with a roller. A characteristic 
of marl is that after being thus packed the material re-cements it¬ 
self, forming a uniform surface. The marls used for roads include 
several varieties. A form frequently used is an amorphous marl 
found usually in old swamps. Marls of this character were for¬ 
merly used extensively in Orange County, being obtained in the 
western part of the county. Marls used in Brevard County-, west 
of Titusville, are of a similar character. The swamp marls are usu¬ 
ally of local occurrence and may be expected in almost any part of 
the State. Some of the limestones of the State are sufficiently soft 
to serve as marls. Thus the extensive formation known as the 
Ocala limestone is, as a rule, comparatively soft, and is extensively 
used for road making, being commonly classed as a marl. The 
marl roads of Marion County are made from this limestone, nu¬ 
merous pits being opened in the county for this purpose. 
Crushed stone is being used somewhat extensively for roads. 
For this purpose hard limestone, flint, or phosphate rOck is used. 
After crushing, the coarser material is spread on the road, making 
a secure foundation, on which the fine siftings are used thus filling 
in and making a top dressing, giving a smooth surface and a very 
durable road. 
SHELL ROADS. 
Shell deposits are less uniformly scattered over the State than 
marl and limestone and are less extensively used for roads. The 
principal shell deposits are the oyster shells found near the coast or 
along inlets from the coast, and the chief supply of these is afford¬ 
ed by the shell mounds accumulated in the past by the Indians, al- 
