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Downloaded from http://trngl.lyellcollection.org/ at Yale University on June 28, 2015 254 TRANSACTIONS OF THE GEOL. SOC. OF GLASGOW. effects were, perhaps, less powerfully felt in the neighbourhood of the Ben Leister Glen; the existing lines of fracture were easily acted upon by the subsequent convulsions; the solid claystones in the former fissures were rent asunder from the incompatible sandstones against which they rested, and the rapid flowing basaltic lava poured into every fissure and crevice that appeared. But, at that period, the now lovely Ben Leister Glen had no existence. A vast level pall of black lava was spread over the whole desolate surface of the land, and the last scene in the history of the Ben Leister claystones was the substitution of the gentle action of water for the desolating force of volcanic fires. The great sheet of lava was cut through: a deep glen was hollowed out in the sandstones that had been entombed below, and the phenomena we witness to-day in the depths of the glen, are probably only a fair sample of what exists throughout the whole of the foundations of the neighbouring hills. XVI. On the CARBONIFEROUS SECTIONS of the LEVERN VALLEY, RENFREWSHIRE. By Mr. HUGH M'PHAIL. (Read February 4, 1869.) Physicalfeatwes of the district—The Levern valley, in the south­ west of Renfrewshire, is bounded on the south by the trappean dis­ trict, which extends over the parish of Mearns and part of Neilston; on the north-west by the Fereneze range, and to the north it flattens out towards the undulating and knolly district south of Paisley. From its western extremity at Crofthead,it gradually opens out towards the Clyde, until it attains a width of more than 2 J miles from Waulkmill glen on the south, to Crookston Mains, where the carboniferous strata are interrupted by an igneous dyke which forms their northern boundary. A line between these two places across the districts of Darnley, Nitshill, and Hurlet may be considered its eastern extremity. A ridge in the centre of the valley, extending from Ward- hill at its eastern extremity, to the west of Barrhead, divides it into two portions, each having its own water-course; the Aurs water united with the Brock, in the southern; the Levern, in the northern. The ridge is formed of thick-bedded sand­ stones which crop out to the north, and are prominently exposed Downloaded from http://trngl.lyellcollection.org/ at Yale University on June 28, 2015 M'PHAIL—LEVERN VALLEY. 255 at intervals' throughout the valley. Kirkton burn flowing from Colinbar glen, crosses the valley diagonally at the western outcrop of the thick-bedded sandstones, and joins the Levern water between Cross-Arthurlie Works and Levern mill. These streams flowing from the high moorland districts in the south, over the trap formations above the valley, together with the various rivulets by which they are augmented, have exposed the various phenomena presented by the igneous and sedimentary rocks of the district. Throughout the valley and along the base of the traps, the physical aspect is indicative of the action of water similar to that observed in other districts in the valley of the Clyde. At the lower end of the valley, the Boulder clay is found in some places only a few inches in thickness, while in others it is raised into mounds, or deposited against northern escarpments, and where it has been deposited between disrupted strata, it has been found upwards of ninety feet in thickness. At Mtshill excellent oppor­ tunities are afforded of examining the Till as it is exposed in many of the quarries. Two-thirds of the boulders in it are of local origin, being composed of varieties of trap, ironstone, limestone, and sandstone, with smaller fragments of coal and clay-shale. The other third belongs to the older formations; they are much rounded, and a few of them slightly striated. In the neighbourhood of Barrhead there are numerous accumu­ lations, evidently fluviatile, or rewash from the Till, which must have been formed while the lower part of the valley was covered. The greater part of Grahamston, which is about 170 feet above sea-level, is built upon such deposits; but, as there have not been any recent excavations, I have neither had an opportunity of examining their nature, nor of determining if they contain any fossiliferous evidences. Carboniferous Strata.—The carboniferous strata come to the surface on both sides of the valley, from the trough in its southern portion. The trough is in a line with a point near the junction of the Aurs water with the Brock, and with Upper Arthurlie Works at the lower end of Colinbar glen, where it has been proved in the coal-workings. It seems at some places to be thrown a little out of the above line by transverse dislocations, one of which crosses it from South Arthurlie to Cross Arthurlie, and evidently causes a slight change of the basin, but in a general view this line may be considered as marking its position. The strata lying Downloaded from http://trngl.lyellcollection.org/ at Yale University on June 28, 2015 256 TRANSACTIONS OF THE GEOL. SOC OF GLASGOW. contiguous to the trap along the south of the valley, and dipping to the trough, are found along the ridge which divides the valley, as they crop out to the north; and in conse­ quence, the beds on the north side of the ridge, are lower in the carboniferous series than those exposed on the south. The strata on the north side gradually thin.out, until the Hurlet main coal crops out at "West Hurlet, and also between Townhead and Blackbyres. Near Townhead a small coal was reached about eleven fathoms below the Hurlet main coal. This coal is about eighteen inches in thickness, and is the lowest stratum which has been reached in the valley. It was also found in the workings of the Nitshill and Lesmahagow Coal Company at Nitshill. The cross section of the valley (given in the accompanying woodcut, page 257), represents the manner in which the strata are found from Waulkmill glen to the igneous interruption at Crook- ston Mains, and embraces more than three hundred fathoms, from the Hurlet and Campsie series upwards to a brown sand­ stone1 in the southern portion of the valley, the position of which I consider to be about twenty fathoms above the Garnkirk lime­ stone. Taking the principal beds in descending order from this sandstone, they are found as follows :— Journal of Strata exposed during the working of the Nitshill Quarries. Feet. In. Feet. In. Sandstone, at its outcrop. Clay shale, with ironstone Coal, - 0 10 nodules, -- 3 0 Sandstone, highly siliceous, 7 0 Oil shale, - -- 0 8 Do. flaggy, - 3 0 Coal, -- 0 10 Clay shale, 2 0 Clay shale, with ironstone Sandstone flags separated by nodules, -- 3 0 shale, - 13 0 Coal, -- 1 6 Sandstone,2 26 0 Clay shale, -- 1 8 Coal, - 1 2 Sandstone, - - 15 0 Sandy shale, 3 4 Shale, - - 0 10 Coal, 10 1 Along the trough from Little Auchinback to near Darnley House lies the above sandstone, terminating abruptly at both ends of the bed, particularly that next Darnley House, where it is seen lying 11 would be inclined to consider this sandstone the equivalent of the mill­ stone grit, if its existence be admitted in Scotland. 2 m There is a part of this bed, averaging about six feet in thickness, highly siliceous, which causes much trouble and expense in the working of the quarries. Downloaded from http://trngl.lyellcollection.org/ at Yale University on June 28, 2015 CROSS SECTION OP LEVERN VALLEY FROM WAULKMILL GLEN TO CROOKSTON MAINS. a, Outcrop of the thick-bedded sandstone on the south of the valley; /, Outcrop of the thick-bedded sandstone to the north, and where it forms the ridge in the centre of the valley; b, Fault seen in Waulkmill Glen ; c, Junction of the Aurs with the Brock ; d, North Brae, or Arden limestone cropping to the north; e, The great fault in the centre of the valley; g, Fault running from Priesthill towards Boghall; h, Horizon of Nitshill sandstone beds; i, Fault between Nitshill and Hurlet sections; j, bed of the Xevern; Is, Outcrop of Hurlet main coal series, with intrusion of igneous rocks. Downloaded from http://trngl.lyellcollection.org/ at Yale University on June 28, 2015 258 TRANSACTIONS OF THE GEOL. SOC. OF. GLASGOW. upon a thick bed of clayey and calcareous shales, which separates it from the limestone locally known as the "North Brae" limestone. Entering Waulkmill glen from the junction of the Aurs water with the Brock, the above shales are well seen, the stream having worn considerably into the rising ground forming its west bank. The upper thirty feet of these shales is a com­ plete mass of nodules; towards the centre they are more clayey, but gradually become calcareous and fossiliferous as they approach the limestone. Further up in the bed of the stream the lime­ stone, whieh has been much wrought in the vicinity of the glen, crops out from under the shales. At a depth, which varies from three to five fathoms from the limestone, there is a " splint" coal of inferior quality, known in the district as the "North Brae" or Auchinback coal, it having been extensively wrought on the grounds so named. The workings were all near the outcrop, the coal varying from three to three-and-a-half feet'in thickness. About a hundred yards from the junction of the Aurs with the Brock, this coal was reached at about eighteen fathoms, being considerably in the dip of the other shafts, and from three to five feet in thick­ ness, gradually becoming thicker towards the trough.

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