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 GEOLOGY The Cannel Mine, which occurs some way above it, is remarkable in that it consists of a basal layer of bituminous coal and an upper layer of cannel which has a thickness of 3 feet at Wigan and thins away in all directions from it ; the common coal thickens as the cannel diminishes. The coal itself has yielded numerous remains of fish-teeth, spines, scales, &c., as well as large Stigmarian roots. The Trencherbone is of good quality in some parts of the area, whilst in others it contains so much dirt as to prove unworkable. At Tyldesley it is associated with a bastard cannel. It is in great demand as a house coal, and large quantities are sent into Manchester and other towns. The Doe Mine and Rams Mine are also good and in great request. The Worsley Four-Feet, which marks the upper limit of the Middle Measures, has been worked at Leigh, Pendleton, and other places, and is a good coal. A great fault known as the Irwell Valley Fault cuts through this area from the Millstone Grit, north of Bolton, in a south-east direction to Manchester, along the line of the valley of the river Irwell ; the downthrow is to the north-east, and is over one thousand yards. The various seams given on the section abut against the fault in regular order from north to south on the upthrow side ; on the downthrow side the seams are shifted to the northwards, and a narrow tongue of the Trias runs up into the middle of the coalfield. (C) WIGAN AND ST. HELENS AREA The St. Helens district forms the most westerly section of the South Lancashire Coalfield, that of Wigan lying between it and the Bolton area. In this area, as in that previously mentioned, the Middle Coal Measures are about 1,000 yards in thickness. Notwithstanding their nearness only two seams of St. Helens — the Little Delf and Rushy Park — have been directly correlated with two of Wigan, viz. the Arley Mine and Smith Coal. The remaining seams are not equally capable of correlation owing to the changing character of the coals themselves, to alterations in thickness and character of the intervening non-productive measures, and to extensive faulting. 1 Comparative Coal Series at St. Helen's and Wigan St. Helen's Lyon's Delf Measures London Delf .... Measures Potato Delf (with partings) Ft. In. 2 8 55 2 86 5 Measures Earthy Coal (with partings). Measures with Coal, 2 ft. 41 6 121 Coal (with partings) 6 Measures i57 St. Helen's Main Delf .... 9 Measures 9 Cannel 2 Measures i8 Four-feet Coal 3 Measures 5^ Pigeon-house Coal 2 Measures 271 Ravenhead Higher Coal. „ Warrant .... „ Main Delf. . . Measures Bastion's Coal Measures 3 4 7 66 4 22 o 6 2 3 9 2 6 8 •) 2 2 o o o 1 9 3 o Wigan Coal-seam of Red Rock Brow Riding Mine Measures Ince Yard Mine .... Measures Ince 4-feet Mine .... Measures with 3 coal-seams. Ince 7-feet Mine .... Measures fWilcock or ( Coal 2 ft. 11 in. Furnace Clay o ft. 6 in. Coal i Coal i ft. 8 in. Measures Pemberton 5-feet Mine Measures Little Coal Measures Pemberton 4-feet Mine .... Measures 387 Wigan 5-feet Mine 5 Ft. 4 3 36 2 108 3 150 6 71 252 5 30 2 45 4 Measures Wigan 4-feet Mine Measures. . . 90 4 72 1 'Geology of the Country around Wigan,' Mem. Geol. Survey, by Prof. E. Hull (1862), p. 12. I 17 In. 6 8 o 6 o 6 9 o 5 9 6 I 6 o o o o o