Joseph Beete Jukes

“ On the north side only, however, has it been followed under the basalt, and that for but a very slight distance; and in every instance in which this has been attempted the coal has been found to be "blacked" and to be fractured, and frequently to pass into "rock and rig." A coal is said in this district to be "blacked" when, by its near proximity to an igneous rock, it has become so altered as to lose all its brightness, and nearly, if not quite, all its inflammability. ”

“ In all cases the isolated masses that are found in the higher parts of the Coal-measures are. I believe, basalt, while the wide spread horizontal sheets of igneous rock that spread over such large areas below, and occasionally make their appearance at the surface where the lower measures crop out, as about Wednesfield and to the east of Pouk Hill, are greenstone. ”

“ It is no doubt founded in fact; the greater the thickness of the intruded trap rock, the more intense, probably, would be the squeeze, and the consequent contraction suffered by the adjacent beds. Beds of coal, too, might certainly be nearly or altogether annihilated by the intrusion of molten rock, but we cannot conceive sandstone or clunch being thus destroyed. ”

“ The Rowley columnar basalt seems to he at a height of about 600 feet above the Thick coal, that of Barrow Hill is apparently at a much less height. If they are each contemporaneous with the beds in which they lie, it follows that the Barrow Hill trap is older than that of the Rowley Hills. Immediately east of the hill, it appears, from the marks of old workings, that a piece of Thick coal cropped to the surface, and was worked in open work along it. ”

“ 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. ”

“ Might not these ideas lead us astray, if we reasoned from them as to what would take place at some depth in the earth, unless we made allowance for the total or nearly total absence of air, and the effect of the covering of rock, which would greatly obstruct the dissipation of the constituent gases of the substance acted on, rendering that dissipation very difficult and therefore very small? ”

“ It seems to me quite possible that portions of the consolidated basalt may have been squeezed for some distance up into the fissures, and still more likely that some of the more decomposed parts (the clay or wacke, which often forms the covering of the hard rock) may have been so squeezed, at least as far as it was possible to follow it in underground explorations. ”

“ Large intrusive masses of this white trap also are found in the pits near Birch Hills Hall, north of Walsall. At Union colliery, north of that, the Bottom coal is cut entirely out by "green rock;" and at Goscott, still farther north, there are six yards of "green rock" resting directly on the Bottom coal. White rock trap just shows itself in the cutting of the Cannock railway south of the bridge in the lane leading from Landywood to the turnpike road. ”

“ A boss of it rises to the surface, cutting up through the New mine coal at the Heath colliery north-east of Wolverhampton, and a little north of that a large mass of it rises broadly out and forms the surface of the ground all around Wednesfield, as delineated in the map. In the Bentley district the basalt of Pouk Hill seams merely to be an irregular swelling of the bed of "green rock" that crops out a little further east along the bank of the canal. ”

“ In which we find the increase in the total thickness to be very nearly in direct proportion to that of the green rock. [8]
In an open work in the New mine coal, some years ago, on Wednesfield Heath, a dyke of the white feldspathic-looking trap was seen cutting up into the coal from below, and ending in some black shale. In some quarries north of Willenhall the same rock may still be seen in veins cutting through the Coal-measures. ”

“ Moreover, the presence of so large a percentage of carbonic acid and water shows that the rock has now a different composition from that which it possessed before the period of injection, when it was in a molten condition. It is, in fact, an altered rock, altered by having had so much carbon, oxygen, and hydrogen added to it as to give it a percentage of 20.330 of carbonic acid and water. ”

“ The same may be said in general of the sheets of "green rock" proceeding at a higher level from Barrow Hill. In each case the "green rock" crops out to the surface, along with the beds in which it lies; although as its thickness is very irregular, and as it shifts its place now and then in the beds, cutting up or down within certain narrow limits, above or below a particular set of beds, that outcrop has a corresponding irregularity and want of continuity. ”

“ This piece lay in an angle between the Corbyn's Hall fault and another, which is supposed to run south of Barrow Hill. In the workings to the west of Barrow Hill the coals are found to be "blacked" as they approach it, and beds of "green rock" (horizontal dykes) are found between the measures to the east for a distance of about two miles.
Pouk Hill.—Pouk Hill, near Walsall, is another mass of columnar basalt of less size than Barrow Hill, but equally, or still more, interesting.
It lies altogether below the Thick coal and between the Fireclay and the Bottom coal. ”

“ This bed is found in the underground workings for about half a mile to the westward of Pouk Hill, and for the same distance to the northward, varying in thickness from 20 feet to 40 feet, lying always just above the Bottom coal, which is often greatly injured by it. It does not extend as far east as the Birch Hills, [7] nor far north towards Bloxwich, nor beyond Clark's-lane to the westward, neither was any found in Messrs. Bates's pits at the Trentham colliery between Mumber-lane and Wednesfield.
Near Wolverhampton none has been found in the Rough Hills. ”

“ I would, therefore, by an eruptive rock mean only such a rock as could have been ejected out of the earth and poured over its surface, whether that surface was there covered by air or by water. ↑ Mr. Walker, jun., who superintended the works of this tunnel, was good enough to let me see a large section constructed from the workings, from which the above statements were taken. ”