Page:The South Staffordshire Coalfield - Joseph Beete Jukes - 1859.djvu/144

126 from vertical to horizontal was in one part more abrupt and in another seemed to have been more irregular. The state of the working of the quarry, too, obscured the relation of the columns on that side. A number of uncompressed spheroids of basalt appeared in one part along the line of junction of the vertical and horizontal columns.

On the south-east side of the quarry the black shales of the Coal-measures might be seen reposing on the basalt, which just below them consisted chiefly of uncompressed balls of basalt, bedded in a mass of decomposed basalt or basaltic "wacké" or clay. A small cutting for a tramway led from the quarry south to the canal, and following down this the Coal-measure shales containing ironstone were seen lying nearly horizontal. At one part these shales were traversed by a small dyke of white rock trap cutting across them at an angle of about 60° with the horizon, and rather more than a foot in width. Farther down this cutting, in consequence of a slight rise in the measures, the basaltic clay earth containing balls of basalt again made its appearance for a few yards, and then finally sank out of sight towards the south.

The columns of Pouk Hill, doubtless, assumed the radiating form above described in obedience to the rule they are known generally to follow, that, namely, of always striking from the cooling surfaces of any mass towards the interior. Thus, in a horizontal sheet the columns are vertical, in a vertical dyke the columns are horizontal, and in a spheroidal mass the columns seem to radiate from the centre, or in other words strike from all sides towards it.

Netherton.—A mass of basaltic trap is very well seen in the canal cutting south of Netherton church, where it is exposed by the rise of the beds below the Thick coal, and is seen to send wedge-like masses into the Coal-measure sandstones.

Sheet-like masses of " green rock" (the local name for the greenstone) seem to spread almost uninterruptedly in the lower Coal-measures from the base of the Rowley Hills and Barrow Hill, through the centre of the district up to Wolverhampton. Bilston, and Bentley.

At Barrow Hill Coppice pits 64 feet of "green rock" penetrated the Gubbin-stone measures just beneath the Thick-coal. At the Birds Leasowe colliery, near Tansey Green, the Thick-coal was found to be "mingled with rock and rig;" and, below the Gubbin measures, "green rock" was found, into which they sunk 38 feet. Between Tansey Green and Shut End furnace the "green rock" is only 36 feet thick, and comes in in the place of the Heathen coal, the Thick coal itself being blacked. To the east of Barrow Hill a sheet of "green rock," which at first is more than 60 feet thick, but afterwards thins to about 30 feet, stretches for at least two miles in one direction. Its usual place is between the Heathen coal and the Whitestone measures, but between Cooper's Bank and the Fiery Holes the "green rock" cuts down under the Whitestone measures. This "green rock" crops regularly out like