464 



THE GEOLOGIST. 



cashire wherever they occur. A series of great " faults," or dislocations, 

 running almost parallel with each other in a N.N.W. direction, and nearly- 

 equidistant, divide the coal-field of Wigan into a succession of belts. Minor 

 faults branch away from the main faults in all directions, and break up the 

 strata into numerous subdivisions. Moreover, each fault and branch fault 

 has a certain and considerable inclination to one side or another in its 

 course, varying from one to three vertical to one horizontal. Hence every 

 locality requires to be " proved," either by boring or by the sections of ad- 

 jacent collieries, so that in sinking a shaft the miner may avoid faults, and 

 " win," at the least outlay, the greater number of seams of coal. The forces 

 which occasioned the dislocations have diminished in power northwards, 

 and the extent of their "upthrows" and " downthrows " vary over the 

 field in question from a few yards to upwards of six hundred. The effect 

 of great upthrows has been the loss of many valuable seams in some loca- 

 lities, and that of downthrows to preserve them, while their combined re- 

 sult has been in one part of the field or another to cause every seam to 

 have one or more " outcrops." The courses of these " outcrops " are clearly 

 traced on the recently-coloured maps of the G-eological Survey, and some 

 of the most favourable situations for viewing them, as well as sections of 

 the district, are given in the memoirs of that survey, by Mr. Hull. The 

 coal-bed roofs of the lower measures of Wigan include remains of drifted 

 plants and Sigillarise, and, in the under-clays, Stigmaria. The " floors," 

 or under-clays of the coal-beds of the middle measure abound with Stig- 

 marise, or the roots of Sigillarise, the stems of which occasionally intersect 

 a coal-bed, but are generally found in the roof. Especially is this the case 

 in the roof of the Four Feet Ince Mine, where, from their upright position 

 and ponderous weight, and the nature of the roof itself, they are the fre- 

 quent cause of melancholy accidents. The coal-beds themselves are vast de- 

 positories of fossil vegetation, the forms and tissues of which are for the most 

 part obliterated ; but in the roofs are found, beside Sigillarise, numerous 

 Ferns, Asterophylites, Calamites, Lepidodendrons, and Coniferse. The 

 fauna of the Lower Coal-measures of Wigan furnish Anthracosia, Modiola, 

 Groniatites Listeri, and Aviculo-pecten jpapyraceus. In the roof of the 

 Lower "Mountain Mine " is a fish-bed containing bands, full of C} T pris or 

 Cythere, Microconchus carbonarius, Anthracosia, and more rarely Gronia- 

 tites, fish-bones, scales, teeth, etc. The middle series contain Anthracosia 

 robusta in abundance, and the varied remains of two fish-beds, one over 

 the Arley and the other over the Cannel mine. From Mr. Hull's memoirs 

 we learn also that the late Mr. Peace, mining-agent to the Earl of Bal- 

 carres, collected from the latter bed beautiful specimens of fish, of the 

 genera Megaliehthys, Holoptychius, Diplopteris, Ctenoptychius, and some 

 large dorsal rays. Some idea of the immense value of this coal-field may 

 be deduced from Mr. Hunt's Mineral Statistics for 1861. He gives the 

 total quantity of coals raised that year in the United Kingdom as 83,635,214 

 tons, of which 12,195,500 tons were raised in Lancashire. The number of 

 collieries (not pits) then in Lancashire was 375, the proportion in the 

 Wigan district being 78. An uniform average quantity for each colliery 

 would show the produce of the Wigan coal-field that 3 T ear to be about 

 3,000,000 tons. Eight shillings per ton at the pit's mouth, — a low enough 

 estimate for Cannel and all sorts, — would give £1,200,000 as the produce of 

 the mines for one year. The facilities at some of the Wigan collieries for 

 executing extensive orders for shipment in a very short time are surprising. 

 At Rose Bridge Colliery, for instance, the property of Messrs. Case and 

 Morris, Mr. Bryham, the able and obliging manager, states they can raise 

 with ease a thousand tons per day, or fifteen hundred tons in the twenty- 

 four hours, by working night and day. 



