90 REPORT—1863. 
their oceutrence. More particularly they wish to show that some of the phe- 
nomen *xhibited by the mining-operations carried on in this district most ma- 
terially bear on this question. They state that the numerous opportunities which 
haye occurred to them of collecting information respecting those superficial 
gravels, clays, and sands which are spread over the coal-field of Durham, and 
slsu the frequent opportunities they have had of observing the abrasion or denu- 
dation of the strata of the district, and especially of a remarkable one locally 
termed “the Wash,” which cuts through a considerable portion of the Durham 
coal-field, have induced them to lay the result of their experience before the 
members of the British Association. 
It was stated by the authors that this wash or drift can be traced through the 
coal-field, from the vicinity of the city of Durham, in a spe direction, to the 
river Tyne, near Newcastle; that it is traversed a considerable portion of this 
distance by the present valley of the Wear, until, having passed Chester-le-Street, 
it follows the course of the Team valley, and terminates at the junction of the 
latter stream with the Tyne. This communication was illustrated by a plan of 
the whole district traversed by “the Wash,” and a series of cross-sections exhibit- 
ing in detail the depth of the denudation of the strata, the nature of the deposits, 
and other information relative to the materials accumulated in this old valley. 
The details of the various cross-sections show that the deepest portion of the 
denudation was along the eastern or dip side of the valley, and that the basset- 
ing or outcropping edges of the strata on that side are more upright and abrupt 
than those on the opposite side; that all the stones and pebbles, from their 
rounded appearance, bear marks of long exposure to the abrading action of water 
in motion; that no traces of shells, bones, or other organic remains were observed ; 
and that the pavement or bottom of the valley on which the accumulated ma- 
terials rest bears evidence of the great power of the water which carried the débris 
along its channel. The surface of some of the harder sandstones met with in 
sinking through the gravel and clay was furrowed and polished in rough and 
scarred outlines, and the coal-seams, where exposed, were either upright, adjoining 
the denudation, or worn and rounded off, as if acted on by the movement of 
harder bodies across them; but frequent cases. occurred where the seam of coal, 
when traced to its termination against the clay, had the upper portion of it de- 
stroyed by abrasion, and portions of that nearer the floor remained, the intervening 
parts being filled up with clay, and boulders, and broken pieces of coal, frequently 
of a large size. The rounded boulders and pebbles found disseminated and mixed 
with the masses of clay consist generally of hard sandstone, limestone, iron- 
stone, &c., of the carboniferous strata occurring to the westward. The lowest 
at of excavation of this valley, being 140 feet below the sea-level, points to a 
ormer higher elevation of land than at present. 
The authors suggest that the feeders, by which the body of waters found their 
way into “the Wash,” may be traced in the shape of branches or tributaries in 
more than one direction. One extends up the rivulet of Urpeth, another from 
Durham to Bishop Auckland and westward on the line of the river Wear, and 
another probable branch extends considerably more to the east, although the 
authors suggest the flow from the latter may possibly have been in a southerly . 
direction and towards the Tees. 
The authors do not decide whether this denudation has been caused by running 
water or glacial action, though the uniformity of the bed of the denudation and 
its moderate rate of inclination would lead to the latter opinion. They would 
not, however, lose sight of the fact, that a body of water which could cover the 
top of the deep deposit, 300 feet thick, which occurs at Durham, must have had 
some effect in the production of a current of considerable force down the course 
of the Wash. 
The peculiar relation of the Wash to the existing river-systems and present 
drainage of the country is also pointed out, and a comparison is made of the uni- 
form rate at which the present river Wear and the old Wash channel decline to 
the north, until the Wear suddenly leaves the line of the old valley and flows to 
the sea through a gap in the magnesian-limestone escarpment, branching off at an 
elevation of 100 feet above the level of the Wash, through the solid strata. 
