170 ARTESIAN WELLS ON THE ATLANTIC COAST. [bull. 138. 
in the Mesozoic (Potomac) strata. This is indicated by the presence of 
the pebbles, * * * and the variegated strata give us another 
proof that the beds at 874 feet are Mesozoic, for many of the Mesozoic 
strata along the eastern border are strikingly variegated." 
In 1891 I secured an order from the Chief Engineer of the Army at 
Washington and visited Fort Monroe for the purpose of examining the 
borings. Having spent several years in studying the outcrops of the 
beds, I believed I could recognize the strata penetrated by the well. 
It was found, however, that the greater part of the borings were lost, 
but fortunately a series from GOO feet to 877 feet were remaining. Por- 
tions of these were secured, and have been studied with considerable 
care. They are in greater part light greenish and brownish clays, 
which are not distinctive, and I could not form a judgment as to their 
age. The 877-foot sample is a mixture of fine sand and clay of dirty 
gray color, containing moderately small angular quartz grains; the 
865-foot and 811-foot samples were more argillaceous. 
At Richmond and along the western border of the Coastal Plain belt 
the infusorial series of the Chesapeake formation is of moderate thick- 
ness and lies in greater part near the base of the formation, but east- 
ward it is now known to thicken, and to comprise a considerable series 
of dark, heavy clays of various kinds. Whether this relation is due 
to the overlap of older Miocene deposits or to an ascent of the diatom 
fauna through the formation is not yet definitely determined, but the 
overlap is probable. The thickness of diatomaceous beds is at least 
300 feet eastward, but from the records as above given and the samples, 
I could not determine their limits in the Fort Monroe borings. It is 
probable that the lowest beds recorded are of Potomac age, but the 
evidence is not conclusive. I believe we should expect the Severn for- 
mation and, probably also the Magothy formation, in the Fort Monroe 
region, as in the Crisfield well. 
In a boring j List completed at the Chamberlain Hotel at Fort Monroe 
a good supply of water Las been obtained at a depth of 915 feet, 38 
feet deeper than the old boring at the fort. It is reported that the flow 
is 78,000 gallons per day and the water rises about 10 feet above the 
surface; a larger supply can be obtained by pumping. The water is 
" slightly saline." The water horizon is thought to be Potomac, but its 
relative position in the formation is not yet ascertained ; possibly it is 
Magothy which furnishes the saline water in the deep Crisfield boring. 
The well affords important encouragement for deep-seated water sup- 
plies in the southeastern portion of Virginia. 
As neither the thickness of the Potomac in this region nor the precise 
depth to its surface is known, I can give only approximate figures, but 
it is believed that its basal beds on the granite bedrock should be 
expected at a depth less than 1,350 feet at Fort Monroe; whether they 
will be found to yield large supx>iies of good water remains to be 
determined. 
