THE ARTESIAN WATER SUPPLY OF EASTERN FLORIDA. 
149 
this well was taken January io, 1910, and was found to be 15 
pounds. The elevation of the well is approximately 8 feet above 
the River. This, together with a pressure of 15 pounds 
would give the well a head of 42.65 feet above the level of the water 
111 the St. Johns River. 
RIVERDALE. 
Riverdale is a settlement along the St. Johns River in south¬ 
western St. Johns County. At this place several artesian wells have 
recently been drilled. A well 302 feet deep was sunk in 1909 by 
Mr. R. C. Walker for the Riverdale Land Company. This is a six- 
inch well and is cased 107 feet. The well is reported to have a 
head of 33/4 feet above the surface and the surface elevation 
above the St. Johns River is estimated to be 8 feet which gives the 
well a total head of 41J 4 feet. The first rock encountered was 
at a depth of 175 feet and at this depth the water was found to 
be under sufficient pressure to rise to the surface. An increase 
in the flow of water was reported at a depth of 190 feet. 
Mr. R. C. Walker completed on February 1, 1910, a well for Mr. 
J. D. Clark. This well is six inches in diameter, 318 feet deep 
and is cased 136 feet. At the depth o i f 174 feet a one foot stratum 
of bluish clayey limestone was encountered. An increase in water 
is-recorded at the depth of 200 feet, from which depth the first flow¬ 
ing water is reported. The well samples indicate that this flow 
comes from a very hard bluish colored rock and water worn small 
pebbles. Immediately on passing through tins stratum which was 
19 feet in thickness, the Vicksburg Limestone was reached as 
is shown by the presence of Nummulites. This determination was 
made from a very complete set of samples of the drillings from 
this well kindly saved by the driller, Mr. R. C. Walker. This 
limestone was penetrated for nearly 100 feet, the total depth of 
the well being 318 feet. The following is a log of this well con¬ 
structed from the notes and the samples sent in by Mr. Walker. 
Feet. 
Surface sand, yellow in color. Soft water... 0-18 
Light gray sands ..... 18- 30 
Dark gray sands, partly indurated; some clay. .. 30- 44 
Shell, sand and gravel .... 44- 55 
Very dark (almost black), marl, similar in appearance to Miocene 
marls, including shell fragments ... .. .. 55- 63 
Light greenish sandy marl . 63- 80 
Dark green marl, small shark’s tooth observed. 80-100 
Gray sand and shell fragments; water ... ...100-112 
