354 
of a valley, but between Richmond and the sea they extend indefinitely over 
the whole plain on either side of the river. This is not all ; they extend 
over the entire tide-water area of the State, from the Potomac to the 
Roanoke (in North Carolina). -They cover this whole region like a sheet 
150 miles from north to south and 100 miles east and west. They begin 
with this fanlike expansion at the head of tide, and continue to the sea. 
After going a few miles above Richmond the gravels are only found near 
the river, and it is the same above Fredericksburg, on the Rappahannock. 
In North Carolina the same phenomena are reproduced ; the gravels brought 
down the rivers, after they reach tidewater, spread in one continuous sheet 
across the State. I have no doubt it is the same in South Carolina. Now 
this contradicts at once the theory of an excavation, as connected with the 
deposition of the gravels. A similar appearance seems to be presented in 
what Sir Charles Lyell calls the tabular mass of drift on the Hampshire 
coast, in England. 
The gravels which I have described in Virginia were brought down, as 
ascertained by their mineralogical character, from the mountains. They are 
not found on the banks of streams which do not issue from the mountains 
as, for example, the Appomattox. They are found high up on the bluffs 
of the rivers which take their rise in the Blue Ridge and the Alleglianies, 
and when they reached the head of tide they were by some agency dis- 
persed over the whole face of the country to the right and left, until they 
reached the sea. 
I think it possible that below Richmond, and similar points, the rush of 
fresh water in the rivers was met by the waves of the sea, which rolled 
inward at the same time, in consequence of a depression of the coast. The 
fresh water and the salt water met, and at the point of junction the gravels 
were spread far and wide over the present low country of Virginia.* I offer 
this as a mere conjecture ; the subject is full of difficulty. 
It was possibly the same in the valley of the Somme. The gravels occur 
on the French coast, as I have stated, 100 feet above the sea-level. When 
they were left there, the river ran 100 feet higher, and the sea stood 100 feet 
higher. 
As the coast subsided and the sea rose to that level, the river sent down a 
flood of fresh water to meet the incoming waves. There are evidences both 
of the freshwater flood and of the movements of the coast-lines.t 
As to the mannner in which the Somme Valley was formed, I do not 
deem it incumbent to explain it. The valley was there when the gravels 
were spread over it ; it was there at the close of the Glacial epoch. The 
“terraces,” if such there be, were there also. 
* This gravel becomes finer as we go below Richmond, 
t The 100 feet gravel-bed on the coast shows this, and marine remains^ 
have been found at Abbeville, 25 feet above the present bed of the stream. 
