STRATA WERE ONCE CONTINUOUS ACROSS THE VALLEYS. 241 
from its shortness and simplicity be taken as an example of the rest; 
it originates in the green sand, but soon cuts down to the red marl, 
and continues upon it to the sea; in both these respects it agrees 
with the upper branches of the Otter, and with the valleys that fall 
from the west into that of the Axe. 
But in those cases where the lias and oolite formations are inter¬ 
posed between the red marl and green sand, the base of the valley 
varies with the variation of substratum; this may be seen by com¬ 
paring the opposite sides of the lower valleys of the Otter, the Axe, 
and the Char, with the variations of their substrata, as expressed in 
the map. 
The valley of Lyme is of equal simplicity with that of Sidmouth, 
and differs only in that its lower strata are composed of lias instead of 
red marl: but the valleys of Chideock, Bridport, and Burton, being 
within the area of the oolite formation, have their lower slopes com¬ 
posed of oolite subjacent to the green sand; whilst that of Charmouth 
is of a mixed nature, having its western branches in green sand re¬ 
posing on lias, and in some of its eastern ramifications, intersecting also 
the oolite. In the same manner the valley of the Axe has has inter¬ 
posed between the green sand and red marl on its east flank, but none 
at all on its western side, below the town of Axminster. These 
apparent anomalies form no exception to the general principle, that 
the variation of the sides of the valleys is always consistent with that 
which is simply referable to the variation of the substrata, on which 
the denuding waters had to exert their force. It is moreover such 
as can be explained on no other theory than that of the strata having 
at one time been connected continuously, across the now void spaces 
winch constitute the valleys. 
