164 ARTESIAN WELLS ON THE ATLANTIC COAST. [bull. 138. 
to the eastward there appears to be a series of thin layers of rock in 
coarser sands which are of wide extent and are great water bearers. In 
certain wells in the Rappahannock Eiver region some local beds of 
rock also occur above the basal beds. The clays are usually blue and 
very hard. They are often 200 to 300 feet thick, including occasional 
sand partings. The marl varies from a fine-grained sticky material 
full of chalky shells to a mixture of sand and broken shells, but the 
former variety predominates. 
LAFAYETTE FORMATION. 
This caps the plateau levels which constitute the surface of the ridges 
lying between the valleys. It is in greater part an orange sandy loam 
with scattered pebbles and streaks of pebbly materials which increase 
in proportion and size to the westward. Its thickness averages from 
15 to 30 feet, and it is similar to the Columbia formation in being a 
superficial capping with coarser, water-bearing beds at its base. It lies 
on the Chesapeake sands and clays in greater part, but overlaps on the 
crystalline rocks to the west. About Fredericksburg and northward it 
overlaps across the Pamunkey and Potomac formations to the crystal- 
line rocks in most cases, and west of Alexandria it overlies a wide area 
of Potomac formation. 
COLUMBIA FORMATION. 
This caps the terraces along the Potomac, Rappahannock, Matta- 
pony, Pamunkey, York, Chickahominy, James, Blackwater, Nottoway, 
and Merherrin rivers, the lowlands bordering Chesapeake Bay, the 
Eastern shore counties, and all of Norfolk and Princess Anne counties. 
Its thickness varies from 10 to 30 feet, and it is merely a superficial 
capping. At its base there are usually coarse material's, consisting of 
gravelly sands or gravel, which contain the water that supplies shallow 
wells in the low-lying regions. 
WELLS IN EASTERN VIRGINIA. 
It may be seen on reference to the map, PI. XV, that there is a fairly 
large number of wells in the Coastal Plain region of Virginia, and 
most of them have been successful in obtaining abundant water sup- 
plies from very moderate depths. Eastward the higher waters appear 
to cease to be available, or yield only saline water, but the lower water 
horizons promise to furnish satisfactory supplies, as is indicated by the 
success of the well just completed at Chamberlain's Hotel, Fort Mouroe. 
A boring now in progress at Norfolk will throw further light on the 
question, and, it is hoped, secure a water supply. 
I have not been able to obtain as much data regarding Virginia wells 
as I desired, particularly in regard to the nature of the beds penetrated. 
Mr. L. Bude, of Sharps Wharf, Mr. Moore, of Courtland, and Mr. F. E. 
Pearce, of West Point, all practical well borers, have furnished many 
