DETAILED RECORDS. 195 
Potomac — Continued. Feet. 
Fine to medium light-brown micaceous sand and clay 640-650 
Brownish-gray micaceous clayey sand containing lignite 650-661 
Fine to medium pinkish-brown sand with beds of pink, red, and white clay 
and lignite — 661-710 
Medium varicolored sand with lignite,. 710-725 
Coarse, light pinkish-brown sand 725-730 
Light-brown sand, containing many brown granules; also lignite 730-734 
Dark-brownish clay and coarse sand . 734-736 
Medium pinkish-brown clayey sand 736-740 
Brown clay with coarse sand; contains lignite. 740-745 
Medium brownish clayey sand 745-750 
Fine to coarse pinkish-brown sandy clay containing brown granules and 
lignite 750-755 
Medium grayish-brown clayey sand 755-762 
Rig used, jet. Diameter of casing, 8 inches. This well was lost by the slipping of a 
coupling on the casing. Another was drilled 10 feet away. Water-bearing stratum, 720 
to 734 feet. Water rises nearly to surface, but flows over casing at and after high tide. 
Yield by pumping, 20 gallons per minute. Water is alkaline, yellowish brown in color, 
contains iron, has a slight odor of sulphur, and is distilled for drinking purposes. Mouth of 
well is 11 feet above mean low tide. 
FLORIDA. 
223. Well at Jacksonville, Duval County. 
[Well begun August, 1903; completed October, 1903. Authority, R. N. Ellis, superintendent water- 
works. No samples preserved by Survey. 1 
The sand and gravel penetrated from 15 to 35 feet are probably of Pleistocene age. The 
formations lying below, it is believed, are late Tertiary, though the water-bearing limestone 
at the bottom may be equivalent to the Vicksburg (lower Oligocene). The beds, as shown 
by samples from neighboring wells, differ from those penetrated by deep borings at Savan- 
nah and other points on the south Atlantic coast in the large proportion of limestone. 
The beds from 750 to 860 feet, described as rock, are limestone or silicified phases of it; 
probably other "rock" beds are also. The "black gravel" mentioned in various beds 
from 50 feet down to 470 feet is most likely dark, fine and coarse, smoothly rounded 
nodules of uncertain origin. 
Well at city waterworks, Jacksonville. 
Feet. 
Filled ground and sand 0- 15 
Varicolored gray to red sand 15- 34 
Gravel 34- 34| 
Yellowish fossiliferous rock 35- 40 
Gravel with water 40- 44 
Gray fossiliferous rock 44- 53 
Clay with thin layers of white rock 53- 58 
Blue clay with black gravel at 58-70 and 82-89 feet 58-89 
Rock 89-94 
Blue clay with black gravel 94-100 
Rock, 2 inches thick 100 
Blue clay with quartz sand and very fine black gravel 100-1 30 
Very hard compact clay and sand 130-142 
Greenish sandy clay 142-204 
Greenish sandy clay with more or less black gravel and occasional streaks < f 
pure clay. ....". 204-250 
Sticky clay with sand and fine gravel 250-263 
