304 
EOCENE PERIOD. 
[Ch. XXII. 
been invariably brought back again to the opinion, that the 
chalk was originally continuous, on a more deliberate review of 
the whole phenomena. 
It may be useful to consider the only other alternative of the 
hypothesis before explained. If the marine groups, Nos. 1, 
2, 3, were not originally continuous, it is necessary to imagine 
No. 77. 
1, Chalk and Upper green-sand.! 4> WeM clayt ] 
2, Gault. > Marine. >Fresh-water. 
3, Lower green-sand. J 5 » Hastings sands. J 
that they each terminated at some point between their present 
outgoings and the secondary strata of the Forest ridge. Thus 
we might suppose them to have thinned out one after the other, 
as in the above diagram, and never to have covered the entire 
area occupied by the fresh-water strata, Nos. 4 and 5. 
We grant that had such been the original disposition of the 
different groups, they might, as they gradually emerged from 
the sea, have become denuded in the manner explained in the 
last chapter, so that the country might equally have assumed its 
present configuration. But, although we know of no invincible 
objection to such an hypothesis, there are certainly no appear- 
ances which favour it. If the strata Nos. 4 and 5 had been 
unconformable to the Lower green-sand No. 3, then, indeed, we 
might have imagined that the older groups had been disturbed 
by a series of movements antecedently to the deposition of 
No. 3, and, in that case, some parts of them might be supposed 
to have emerged or formed shoals in the ancient sea, interrupt- 
ing the continuity of the newer marine deposits. But the group 
No. 4 is conformable to No. 3, and the only change which has 
been observed to take place at the junction, is an occasional in- 
termixture of the Weald clay with the superior marine sand, 
such as might have been caused by a slight superficial move- 
ment in the waters when the sea first overflowed the fresh- 
water strata. 
