Kendall: The Concealed Coalfields of Yorkshire , elc. 197 



The area was divided in 187 1 into a tract of 672 square 

 miles, whicii was estimated to contain an average thickness of 

 forty feet of coal at a workable depth and another tract of 

 232 square miles computed to yield twenty feet of available 

 coal. 



No attempt was made to delimit these two regions, and it is 

 therefore impossible to say from which one the now proved area 

 should be deducted. It is, however, probable that the estimate 

 of thickness erred considerably on the side of excess. 



4. What grounds, if any, are there for extending the limits 

 of the concealed coalfield? 



The many borings and sinkings which have been put down, 

 chiefly for water, but partly in search for coal or other mineral, 

 in the country between the visible coalfield and the East Coast 

 have made it quite apparent that the concealed portion has 

 a much wider extension than the most sanguine estimate of 

 1871 admitted. 



New methods of inquiry have also been devised or old ones 

 extended and systematised, and these have provided a more 

 scientific plan upon which to proceed than the entirely empirical 

 basis of the earlier calculations regarding this coalfield. 



The borings and sinkings have furnished the data for 

 approximate determination of the thickness of each rock forma- 

 tion covering the Carboniferous rocks in the area, and several 

 have pierced to the Coal Measure or older rocks, giving precise 

 information in such cases. 



The York, Derby, and Nottingham coalfield lies in a basin- 

 fold, of which the western edge and a small portion of the 

 northern margin are exposed, the remainder of the basin and 

 its edges are concealed beneath a discordant sheet of newer 

 rocks, steadily increasing in thickness to the eastward by the 

 successive on-coming of layer upon layer of eastwardly dipping 

 beds. 



The problem which has to be solved is the determination of 

 the place and mode of uprise of the other edges of the coal- 

 basin, beneath a mantle of newer rocks, hundreds or perhaps 

 thousands of feet in thickness. 



The n-iethod adopted by the late Prof. Green in his evidence 

 to the last Commission was to assume that the axis of the 

 trough coincided with the position of the highest normal Coal 

 Measure rocks in the visible field and to draw an ellipse 

 symmetrically about the edge ot the elongated area in whicii 

 they had been proved. 



190.S July I. 



