630 Mr. Aubrey Strahan [March 17, 



formation. Surface observations made upon the newer formations 

 give no clue to the structure of the coal measures ; reliance has to 

 be placed on boreholes, and on the identification of the specimens 

 obtained from them. The section therefore has been drawn through 

 a borehole at Oxton, and near the Anneslej Colliery now working, 

 to a borehole at Kelham. 



The measures of the visible coal-field contain many workable 

 seams of coal, but for the sake of simplicity I have represented^ three 

 only. Of these the Top Hard is the most important, and the ol)ject of 

 search in the boreholes. The Oxton borehole was put down 7j miles 

 within the margin of the concealed coal-field, and furnished valuable 

 information. It showed that the base of the newer formations 

 descended eastwards 790 feet in that distance— that is, at a rate of 

 1 in 50 — and thus rendered possible a forecast of the thickness of 

 these formations that was likely to be met still farther east. It 

 proved also that the Top Hard had descended 1,170 feet in the same 

 distance, and was therefore more steeply inclined than the newer 

 formations. This gives room for the appearance of higher coal 

 measures eastwards than now exists towards the west ; indeed, in the 

 absence of further information, it appeared possible that the concealed 

 coal-field might extend an indefinite distance, though it might 

 descend to an inaccessible depth. As a fact, its eastward limit was 

 the subject of prolonged consideration by both the Royal Com- 

 mission of 1871 and that of 1905, but neither Commission had 

 sufficient evidence to decide the question. Much light has been 

 thrown upon it by the borehole at Kelham. 



The Kelham Jaorehole, situated nearly ten miles east of the Oxton 

 borehole, proved that the eastward dip of the newer formations was 

 maintained at the same gentle angle. At a depth of a little more 

 than 1,500 feet it traversed a seam of coal, the identity of which is 

 in doubt. At about 1,700 feet it passed through a dyke of igneous 

 rock which is of no significance. More important is the fact that 

 down to about 2,400 feet it was in strata which, by their character 

 and fossils, could be identified as lower coal measures, that below 

 them it met little more than 200 feet of millstone grit, and that it 

 then entered carboniferous limestone. 



More than one interpretation of this section is possible. I have 

 chosen the simplest, and have assumed that the greater part of the 

 millstone grit is cut out by a fault. But whatever explanation is 

 adopted, and whatever the coal-seam may be — whether the Top Hard, 

 as supposed by some, or the Silkstone, as appears more likely — an 

 eastward rise of the coal measures has been proved to exist. The 

 deepest part of the concealed coal-field has been passed, and the eastern 

 limit is in sight. As a fact, the bottom of the trough is probably 

 not far from Oxton, near which place the strata have been found to 

 become nearly horizontal in the workings of the Annesley Colliery. 

 Similar explorations are being carried on across other parts of the 



