172 
LAMPLUGH : GLACIAL BEDS. 
between them is in colour, and though this is so well-marked 
as to enable one to point out with certainty to the exact spot 
where the one ends, and the other begins, yet there are many 
who deem divisions marked by colour to be unsatisfactory, 
and who would therefore look upon this as insufficient 
evidence to warrant a separation. 
Fortunately, however, testimony of a more convincing 
kind is not wanting to show beyond doubt that, even allow- 
ing for possible contemporaneous denudation, a considerable 
time must have elapsed between the formation of the lower 
Purple clay, and of the upper Brown bed. It is also a useful 
illustration of the value, as lines of separation in this part of 
Yorkshire, at least, of these definite colour partings. 
The evidence referred to is found in the presence of a 
broad deep hollow in the lower cla}', between Reighton and 
Hunmanby, which has not only been scooped out, but has 
also been completely filled in again with finely laminated 
sands and warps, in places nearly 40 feet thick, almost free 
from pebbles, save a few coal specks. On each side of the 
hollow, which is 500 yards across, the Brown clay rests 
directly upon the Greenish-Purple clay, but when it reaches 
the southern edge of the hollow, instead of following the 
steep cliff-like slope of the lower clay, it continues along 
the same level, thus admitting the intervention of the lamin- 
ated warps, which completely fill the intervening space. 
These warps at first dip steeply down the side of the hollow, 
and are also slightly contorted towards the top, but for the 
most part they are very even and regular. The northern end 
of the hollow is much obscured by slips ; but shortly after 
the laminated clays cease to be seen in the cliff, a clear section 
shows the two Boulder clays to be once more in contact. 
This Brown clay is strongly developed in the cliff near 
Filey Brig, being there of great thickness, and still resting 
upon Purple clay with a green tinge. 
