206 
FLORIDA STATE GEOLOGICAL SURVEY. 
6, 1910, was eight and one-half pounds or a pressure sufficient to 
cause the water to rise 19.6 feet above the surface. 
PUTNAM COUNTY. 
LOCATION AND SURFACE FEATURES. 
Putnam County lies bordering the St. Johns River. On the 
north it joins Clay County, and on the south Marion and Volusia 
Counties. The total area of the county is 772 square miles. The 
elevation increases inland from the St. Johns River. At Flora- 
home, in the northern part of the county, along the line of the 
Georgia Southern and Florida Railway, an elevation is reached 
of 150 feet. On the Rochelle branch of the Atlantic Coast Line 
Railroad an elevation of 105 feet occurs at Interlachen, in the 
central part of the county. That part of the county bordering 
the St. Johns River includes palmetto flatwoods and some open 
flatwoods. Much of the southern and western part of the county 
is occupied by the lake region, many small, beautiful lakes oc¬ 
curring in this section. 
WATER-BEARING FORMATIONS. 
The data regarding the formations reached by the wells in 
Putnam County is very meager, owing to the fact that few well 
samples have been preserved. 
After passing through the superficial sands in this county, 
calcareous clay and sands are reached, in which are imbedded 
black p'hosphatic pebbles and water-worn gravels. From such 
imperfect information as has been obtained it seems probable 
that some of the wells terminate in this formation and do not 
reach the Vicksburg Limestone. The log of a well at Orange 
Mills, which terminated in loose, clear-grained sand at a depth 
of 160 feet, is given on a subsequent page. A second well within 
a half-mile of this well apparently reached the Vicksburg Lime¬ 
stone at or about the depth of 160 feet. Samples from the well 
of B. F. Dotney, at San Mateo, drilled in 1909, by H. Mervin, 
show the presence of black phosp'hatic pebbles as deep at least 
