22 FLORIDA GEOLOGICAL SURVEY TENTH ANNUAL REPORT. 
larger pieces are first broken by pick or sledge and the material then 
passed through a crusher. After passing through the crusher the 
material, now broken into pieces, one to two or three inches in size, 
is fed automatically into a drying cylinder heated by crude petro- 
leum. These, cylinders which are 30 to 40 feet long and five or six 
feet in diameter, revolve slowly and by means of half cups set at 
an incline move the fullers earth forward with each revolution. A 
high temperature is not sought in the cylinder as used in Florida, 
the object being to remove the surface moisture from the clay. 
The fullers earth passes through the cylinder slowly, each piece 
of clay occupying fifteen to twenty minutes in transit. The fullers 
earth upon dropping from the cylinders after drying is carried to a 
storage bin, and is there fed to the mills for grinding as needed. 
The ground material is passed through bolters and separated into 
the grades desired for commercial purposes. After bolting, the 
earth is sacked for shipment and is labelled according to the de- 
gree of fineness. The grade most used in refining mineral oils is 
about 30-60 by which is meant fullers earth ground to a fineness 
which permits it to pass through a thirty mesh screen but not suf- 
ficient to permit it to pass a sixty mesh screen. The finer grades 
find other uses. 
LIMESTONE. 
The limestones of this area, all of which are of the Chatta- 
hoochee formation, are found principally in the western part of 
Gadsden county along the Apalachicola river. There are, how- 
ever, some limited surface, exposures of this limestone in the north- 
eastern part of this county. 
The Chattahoochee Limestone is extensively exposed in the 
vicinity of River Junction. The. rock here might be termed an 
argillaceous limestone and some years ago was used for the manu- 
facture of a natural hydraulic cement. The output of cement from 
this limestone for the year 1898 is given as 7,50° barrels.* The 
limestones within this area are not at present utilized although in 
Wakulla county, which lies just east of this area, limestones of this 
formation are quarried and sold for road and concrete materia! 
and for agricultural purposes. 
* U. S. Geol. Surv. 20th Ann. Rept., pt. VI (cont.), p. 547, 1899. 
