Geology of England and Wales &c.” 215 
iragments of chalk and flint is interposed ; leading us to 
the conclusion, that after the consolidation of the chalk, a 
partial destruction took place by running water, and that, 
of course, a considerable period must have elapsed between 
the deposition of the chalk and the plastic clay.* 
Subordinate beds of chalk, marle, and fuller’s earth. and 
thin partings, or seams of clay, are found in the chalk stra- 
ta. The numerous layers of nodular flints, and veins and 
tabular masses of the same, so characteristic of this forma- 
tion, are most abundant in the upper layers ; and hence the 
distinction into Upper and Lower Chalk. We extract the 
following ingenious hypothesis of the original production of 
these flints, és 
Aumerous remains of alcyonium and spongia. 
Sate thickness of the chalk beds in England is between 600 
‘nd 1000 feet. 
chalk strata, with all the strata above them, are 
ne i and be- 
are also numerous ravines on the surface of the chalk, 
th the upper or tertiary formations, which appear to have been formed 
by the action ef currents ‘water, perhaps dilavial.—{ Ed. } 
