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BOTTLDER-CLAYS OF LINCOLNSHIRE.
125
entire absence of even ditch-sections prevented my coining to any
conclusion on this point.
The appearances at these three localities being not unfavourable
to the supposition that the brown clays passed into chalky clay,
taken together with the fact of the former clay occurring at so
great a height on the "Wold as nearly 400 feet, inclined me to the
belief that there was no great separation in time between the
formation of the two series. It was not, therefore, till last year
(1883) that I recurred to the opposite opinion, in consequence of
finding evidence on the west side of the Wolds which forced me to
regard the brown clays of that district as belonging to a much more
recent period than the blue and chalky clays. This evidence may
be briefly recapitulated as follows : —
1. The position of the red-brown clays near Brigg resting against
ridges of Jurassic clay, which are capped by outliers of Chalky
Boulder-clay (as in fig. 3), the two clays being very different in
Fig. 3. — Section througJi Low Barf, S.E. of Brigg.
(Horizontal scale : 2 inches to a mile.)
d d
a. Alluvium. b. E,ed Clay, c. Chalky Clay. d. Oxford Clay.
appearance, and the former occupying valleys which appear to have
been eroded out of a surface composed of Oxford Clay overspread
by a sheet of Chalky Boulder-clay.
2. The fact that a red-brown clay of similar type actually rests
upon a continuation of the older Boulder- clay in the district between
Market Basen and Langworth.
3. The manner in which the mottled clays separate themselves
from the blue Boulder-clay and from a terrace or narrow tract along
the western border of the Fenland, between it and the highland,
just as they do between the marshland of East Lincolnshire and the
Chalk Wolds.
To these considerations may be added the following : —
4. The actual superposition of the mottled clay on the blue
Boulder -clay at Boston.
5. The relative positions of the two clays along the north border
of the Pens by East and West Keal, where the Brown Clay is
banked against the slope of hills capped with Chalky Boulder-clay*.
6. The fact that, while both Boulder-clays are found at the same
level south of Bevesby, they each retain their distinctive colours
and characters and occur in separate areas.

• See Section in Quart. Journ. Geol. Soc. vol. xxxv. p. 405.