PROCEEDINGS, 1871—1877. 
365 
Isle of Axholme, Brayton Barf, and Hambleton Hough, as well as other 
places. Upon these Triasic rocks rest the post-tertiary beds, the 
aggregate thickness of which is, in some cases, several hundred feet. 
At the base is boulder clay exposed on the surface as far south as 
Escrick, but occurring much lower down in the valley, at a consider- 
able depth beneath the surface. Above the boulder-clay is a coarse 
gravel, with alternations of sand. A fine section is exposed at the 
railway station at Heck. Resting on the gravel is a bed of laminated 
clay of very constant character over a large area. It has a dark grey 
colour, and splits, when dry, into fine laminse. At Selby it is 48 feet 
thick, and at Cawood 57 feet. It contains no fossils, but from its 
laminated character and its resemblance to modern warp. Dr. Parsons 
is of opinion that it must have been formed in a tidal estuary similar 
to that of the Humber. Above this is usually a bed of sand, and 
then a considerable thickness of peat and forest bed. On Thorne 
Waste, the peat attains a depth of 20 feet, which northwards is con- 
siderably reduced. At Goole, it is only 6 inches in thickness. At the 
bottom of the peat, and rooted in the sand, are innumerable stumps 
of trees ; the majority are Scotch fir ; but oak, willow, birch, hazel, 
and others are met with. Elytrae of beetles and other insects are 
common. Horns of deer have been found, but other animal remains 
have not occurred. The whole thickness of this peat appears to 
have been formed during the historic period, shown by the fact that 
the trees which lie beneath it have been felled by the agency of man, 
which is proved by the marks of tools and of fire on the stumps, and 
felled timber. The uppermost bed of the series is composed of warp, 
a name locally given to a peculiar sediment held in suspension in the 
tidal waters of the Humber and its tributaries. It is probable that 
this sediment is derived from the rapidly perishing coast of Holder- 
ness, and consists of the disintegrated materials of the boulder clay. 
The land adjoining is at a considerably lower level than the bed of 
the river, and this fact has been taken advantage of, for many years 
past, in artificially warping the land. To effect this large drains have 
been cut from the river ; the land intended to be warped is enclosed 
in a high bank, and a communication is then made with the warping 
drain, which allows the water to flow over the land at every tide. 
