Page:The South Staffordshire Coalfield - Joseph Beete Jukes - 1859.djvu/78

60 ¤seems to altogether die out, and 2½ feet of fire-clay alone to interpose between the Sulphur coal and those below it These great variations in thickness seem to take place principally in the sandstone, which, for instance, about Coseley is only 15 feet thick, while it is more than 60 feet not half a mile off. North of Darlaston, between the Ranters* chapel and Darlaston Forge, the New mine rock, having gradually thinned out from Bilston to a thickness of 9 feet only, suddenly swells out to 78 feet with such rapidity that it was described to me at first as a "fault," by which the Heathen coal and upper measures were thrown up 60 feet or 70 feet.

The sandstone known as the New-mine-coal rock extends even as far as the Brown Hills where it is known as the Yard-coal rock, the Yard coal being the upper and separated part of the New mine. The rock is there 30 feet thick.

24. (XX.) .—This coal has its normal development in the district between Wolverhampton and Bilston, where it is very regular, and is always 6 or 7 feet in thickness. It is split into two, occasionally, by a thin parting of batt of some 6 or 8 inches. This parting is a little more pronounced at Monmore colliery, north of Willenhall, In this colliery and the neighbourhood is so remarkable an instance of the phenomenon well known to all geologists as "false bedding," or "oblique lamination," that it is worth while describing it. Several small quarries had been opened in some light-coloured sandstone just above the New mine coal, the same as that just spoken of as the Twenty-yard or New-mine-coal rock, and over a space of nearly a quarter of a mile square, the apparent dip of that sandstone was seen in each quarry to be about 25° to the south-east. The sandstone was fine-grained, with shaly partings, often splitting into flags, and the whole of the lines representing stratification inclined at the tame amount and in the same direction. As I[ knew the coal was worked at a very slight depth over all that space. I could not understand why it did not crop to the surface, till I came on a larger quarry that explained the pnzzle. In this quarry the coal was seen lying as nearly horizontal as possible, with the shaly and flaggy sandstone dipping regularly down on to it at an angle of 25°.—(See Figure 10.)



There was no appearance of any lenticular thickening or thinning of the beds of sandstone, they simply ended against the upper surfaces of the coal, which, when bared, was found to be quite smooth, almost as if polished, but not quite level, forming slight undulations, but with no admixture of any other materials than coal. There were, in some places, about 15 feet of sandstone exposed, and about 8 of coal, the length of the quarry being about 50 yards, throughout which there was no material change in this structure. Like other similar structures in most sandy beds, it shows that the materials must have been brought into their present situation by a pretty rapid current, and that a bank being once produced, the successive accumulations were formed on the slope of it into inclined layers or beds. where we have the following section:—

and about a mile north-east of that, around Bentley, the New mine coal is divided into two by measures which vary from 30 to 50 feet in thickness, composed partly of clay, but principally of sandstone.

These two coals there lose their name of the New mine, and are called respectively the "Yard coal" and the "Five-foot coal," or in some cases the "Four-foot coal," as shown in the following sections:—