160 ARTESIAN WELLS ON THE ATLANTIC COAST. [bull. 138. 
This gravel is at or very near the base of the Potomac formation. 
Lafayette Square Opera House. — The following record is given of the 
well at this locality, Madison place, near H street NW,: 
Feet. 
0-50 loam. 
50-55 sand. 
55-61 clay ; blue, sticky. 
61-70 coarse sand with water. 
70-71 clay % 
Mount Vernon Apartment House. — This well, at Ninth street and New 
York avenue NW., found no coarse beds at the base of the Potomac 
formation, and passed down into the crystalline rocks, where a supply 
of 60,000 gallons a day of "very pure water" was found. The follow- 
ing record is given : 
Feet. 
0-10 surface materials. 
10-50 yellow loam and clay. 
50-65 sand. 
65-133 clay and sand ; stiff clay at base. 
133-183 crystalline rocks. 
North Takoma Hotel, — The well at this hotel has a depth of 251 feet, 
of which about 40 feet at the top are in the Potomac beds, the remain- 
der being in crystalline rock, quite deeply decomposed. 
The Cairo. — The well at this place (Q street between Sixteenth and 
Seventeenth streets W.) is 312 feet deep. It first penetrated the 
Columbia loams and gravels and then disintegrated crystalline rocks, 
from which a fair supply of water is obtained at a depth of about 70 
feet. From 70 feet to the bottom the boring was in hard, crystalline 
rocks which furnished no water. 
Good Hope. — The well now in progress on the summit of Good Hope 
Hill, about 280 feet above tide level, is down to a depth of 380 feet, but 
has not found water. It has not yet reached the Potomac horizons 
which yield water at 240 and 350 feet below tide level at the Asylum 
wells, 2 miles west. 
Highlands. — The well at the hotel has a depth of 96 feet. The water 
is soft, slightly chalybeate, and very cold. The boring is said to have 
passed through clay to 60 feet, then some quicksand, then clay, and 
finally a coarse, nearly white sand containing a large water supply, 
probably from the same bed as that at the Reform School. 
WATER HORIZONS AND PROSPECTS IN THE DISTRICT OF COLUMBIA. 
The deeper-seated underground waters have been tapped by a suffi- 
ciently large number of wells in the District to demonstrate the almost 
general extension of water-bearing beds in the basal and lower bed of 
the Potomac formation, and there is often a fair prospect for finding 
waters in the crystalline rocks. The wells that did not find a satisfac- 
tory water supply in the basal Potomac beds are at the Ice Works, at a 
