196 MESSRS. KIKKBY AND DUFF ON THE 



abandoned quarry which Mr. George Bowes, of Wackerfield, 

 informs me was wrought for road-metal by his father and him- 

 self more than forty years ago, where I found the whinstone as 

 lying in the form of a small oval basin, with the longer axis east 

 and west, and about three-quarters of an acre in extent, and 

 thirty feet deep. The whole of this basin of whinstone was 

 worked out, but a small dyke of the same rock, from six to 

 nine feet wide, was found beneath it, running east and west. 

 The sides and bottom of the quarry are of sandstone much al- 

 tered by heat, and the dyke is still to be seen at the bottom and 

 east end of the quarry, in which direction I traced it for half a 

 mile in a direct course for Bolam. To the westward I could find 

 no indication of it : whether it is continued in that direction I 

 cannot say, but I have no doubt of it being an offshoot from the 

 main dyke, which it evidently joins near the last named place. 

 (J. D.) 



DRIFT. 



A deposit of clay with boulders generally covers the Coal 

 Measures of this district to a greater or less extent. It often 

 partakes more of the character of a local drift than of true boul- 

 der clay. At other times the presence of well striated fragments 

 of Lower Carboniferous rocks, that have travelled from the west, 

 give it an aspect identical with the latter deposit. 



Apparently of later origin than this boulder clay are some 

 thick accumulations of sand, gravel, and fine brick clays, which 

 are found in and on the flanks of the valleys of the Wear, Graun- 

 less, and Tees. These deposits occur over one hundred feet 

 above the present river levels, and in some cases borings have 

 shown that they extend considerably below them. When they 

 are met with underground, as they sometimes are, much to the 

 chagrin of the coal-owner, they are termed a " wash," we as- 

 sume from the coal being washed off before they were laid down. 

 Fig. 20 gives an example of a "wash" in the workings of the 

 Brockwell seam, at the Old Etherley Colliery. A similar instance 

 of denudation occurs in the same seam in the Crook valley, and 

 others have of course been noticed in other parts of the coal-field, 



