219 
exposed, as at Brayton Barf, Carboniferous sandstone 
boulders, lying scattered upon the ground, bear witness that 
the gravel has been removed by denudatioil. A very fine 
section at Heck Station (represented in Fig. 1) shows 
the gravel resting upon the denuded surface of the Red 
Sandstone. The mode of junction is peculiar : the surface 
of the Red Sandstone, which dips at a small angle to 
the south, is eroded into a number of cavities, which 
are filled up level with gravel and sand ; upon the plane 
surface so obtained rests a single layer of pebbles, all about 
the size of the fist, and above this a Isijer, six inches thick, 
of sand cemented with clay into a more coherent bed ; upon 
the plane, and slightly inclined surface of the latter bed, 
rests the gravel, strongly current bedded, and dipping at a 
high angle to the south. Similar sections are seen at Whitley 
Thorpe, and at PoUington ; the gravel at the latter place 
being 20 feet thick, and rising to a height of 60 feet above 
the sea-level. This gravel consists of rounded boulders of 
Coal-measure Sandstone and Millstone Grrit ; the larger ones 
being, as a rule, about six inches in diameter, although I 
have found some as large as 20 inches, together with small 
brightly- coloured chert pebbles. Pebbles of Carboniferous 
and Magnesian Limestone are, so far as I have observed, 
entirely absent. A similar gravel is seen at Thorne. At 
Gateforth House, near Hambleton, the gravel contains a few 
fragments of Magnesian Limestone, and I have found one of 
Silurian slate. At Hensall Station, near Heck, but on a lower 
level, and again in the borings at Newbridge, near Snaith, a 
similar gravel is met Avith, but containing many flat frag- 
ments of Magnesian Limestone, which at Heck is absent. At 
Askern, resting on the Magnesian Limestone, is a gravel 
composed entirely of angular pieces of that rock ; at 
Crowle, resting on the Keuper, is one consisting of the green 
indurated Marls of that rock ; and at Whitton, on the Lincoln- 
i6 
