500 STEVENSON— INTERRELATIONS OF FOSSIL FUELS. 



taining all of the thick coals, consists of reddish, gray, yellow sand- 

 stones and shales with coals and fireclays. The last are rich in 

 Stigmaria. The Coal seams vary much in quality as well as in 

 thickness. In the western part of the area, one portion of the sec- 

 tion contains only unimportant coals but in the eastern part, near 

 Wigan, it has, beside some thin streaks, the Haigh Yard, an excel- 

 lent coking coal, as well as the King and the Cannel. The King has 

 a maximum of 7 feet near Haigh, but thence as a center it thins 

 away toward north, west and south. The Cannel has chief impor- 

 tance near Wigan, where it is 3 feet thick ; but it is a lens, thinning 

 away in all directions and it is represented by ordinary coal toward 

 the eastern border. This and the King coal are almost in contact 

 in a considerable area, but northwardly they separate until the inter- 

 val becomes 60 feet. A cannel, 2 feet 3 inches, is in the St. Helen's 

 section at several hundred feet above the place of that at Wigan, 

 but it disappears northwardly and is represented by black shale at 

 Wigan. 



The Lower Coal Measures, about 1,800 feet thick, consists of 

 micaceous flagstones, shales with thin coals. The fourth seam is 

 the Canister resting on a silicious underclay ; the third is the Bullion 

 Coal in whose roof are the "bullions," nodules of argillaceous lime- 

 stone with Goniatitis. Marine fossils are found in the black roof 

 shales. The Millstone Grit, coarse grits, flagstones and shales, has 

 only two or three thin coals. 



The sandstones of the Coal Measures and Millstone Grit are 

 often reddish. Those of the Grit are in great part crossbedded, 

 while those of the Coal Measures are described as " generally cross- 

 bedded, micaceous, ripple-marked and exhibit sun-cracks, perfora- 

 tions and tracks of annelides and perhaps of moUusks." The roof 

 of the fifth coal of the Lower Coal Measures has vertical Sigillaria. 

 The Lice 4-feet coal, near top of Middle Coal Measures, has thou- 

 sands of vertical stems in its roof throughout the Wigan district. 

 Anthracosia and Anthracopteria are at several horizons in the Mid- 

 dle Coal Measures and marine fossils are abundant in the Lower 

 Mieasures. The Wigan cannel contains MegaUchthys, Holoptychius, 

 Ctenoptychius and Diplopterns. 



No " washout " is noted by Hull or Bolton. 



