﻿Vol. 6 1.] WASH-OUTS IN THE MIDDLE C0AL-MEASTJKES. 341 



occurred at various horizons in the Middle and Lower Coal- 

 Measures; and it is only by defining* these accurately, by survey 

 upon plans, that any intelligent idea can be formed of their origin 

 or probable extension. 



On the accompanying plan (fig. 1, p. 339), the position is shown 

 of a wash-out in the Barnsley Seam, which has been proved to exist 

 from Q, to R — 1700 yards in an east-and-west direction, and by a 

 drift — H to J in a transverse direction. 



In the Parkgate Seam, which lies 240 yards below the Barnsley, 

 another wash-out has been proved, covering the area, as shown by 

 the diagonal shading, for a distance of 2600 yards in length in a 

 north-and-south direction, and found to extend 600 yards in width. 



The thickness of the strata overlying the wash-out in the Barnsley 

 Seam is 650 yards, and in the Parkgate Seam 500 yards. The 

 position is more clearly defined on reference to fig. 2, section 

 M to N (p. 340). 



The Swallow-Wood Seam, lying 60 yards below the Barnsley, 

 has been partly worked under the same area, but no signs of a 

 wash-out have been found, and the section is normal and uniform. 



In order to define more clearly the dip of the measures, and the 

 position of the seams referred to, a section (fig. 2) has been drawn, 

 the line of which is shown in fig. 1. The direction is S. 40 E., 

 and about the true dip of the seams, extending over 3 miles. 



Starting- at the point M, where the Barnsley Seam is 142 yards 

 deep, and, after crossing the well-known Northerly Don Eault 

 (referred to in the Geological Survey Memoir on the Yorkshire Coal- 

 field, 1878, pp. 499-500), the inclination of the strata is half an inch 

 to the yard, and gradually increases until it reaches the point O, 

 where it is 16 inches to the yard; then it decreases in a like 

 manner towards the Silverwood Colliery at N, where the Coal- 

 Measures are practically level, and the Barnsley Seam lies 745 

 yards deep. 



The Baensley Seam. 



Fig. 3, section J H (p. 340), shows a drift driven from the plane 

 of the seam, and proves the disappearance for 150 yards of the coal, 

 the original site of which has been filled up by sandstone of a 

 similar nature to the roof overlying the coal. The coal presumedly 

 has all been stripped and denuded throughout this distance, and 

 it has not been proved to exist in a normal condition nearer than 

 900 yards from the face of the drift marked P on the plan (fig. 1, 

 p. 339). 



The Coal-Measures are much disturbed and contorted, and in some 

 places appear to have been thrust up above their original position ; 

 therefore it is evident that the wash-out took place, or was formed, 

 at a time antecedent to the disturbance. 



The drift has been driven forward 230 yards from H ; at the 

 beginning the sandstone overlies the coal, and a similar bed was 

 found at the end of drift J, at which point the drift was dis- 

 continued. 



Q. J. G. S. No. 242. 2 a 



