230 TRANSACTIONS OF THE [MAR. 15, 



Middle Coal Measures, 



We have already alluded to the broken up character of these 

 Measures, whereby small isolated portions have been dignified 

 with the name of coal fields. The most southerly patch is the 

 Manchester coal fields, a lanceolate area about four miles long 

 from north-northwest to south-southeast and a mile and a-half 

 broad acx'oss its greatest diameter. This coal field, whilst rela- 

 tively insignificant and now unused, is of considerable geological 

 importance, in that the Upper Coal Measures are here in place 

 and well developed. The Middle Coal Measures are deep 

 seated and scarcely touched, owing to the great thickening 

 of the barren measures, below the Four Feet coal of Bradford 

 and Clayton. This latter seam is supposed to be the equivalent 

 of the Worsley Four Foot Seam, which marks the upper limit of 

 the Middle Coal Measures in other parts of Lancashire. At- 

 tempts to reach the thick coals of the latter have thus far failed* 

 and will probably not be renewed until other portions of the 

 south Lancashire coal field are exhausted. Professor Hull is of 

 opinion that at least 616 yards of barren measures will have to 

 be penetrated below the Bradford and Clayton Four Feet seam 

 before a workable coal is reached. 



The Upper Coal Measures which have been worked in this 

 coalfield will be dealt with elsewhere. 



South Lancashire Coal Field. 



This coal field, which is extremeh' irregular and much cut up 

 by faults, can be best dealt with by a division into districts. 



As a whole, iL covers a tract of country thirt3^-two miles long 

 from east to west, and averaging six miles in breadth. f To the 

 north it runs out upon the Lower Coal Measures, to the south it 

 dips under a narrow band of Permian sandstones and marls, the 

 whole being faulted down under the Trias of the Cheshire plain, 

 which runs up into the margin of the coal field in a few broad 

 triangular tongues. To the east as to the north, the measures 

 run out upon the Lower Series, whilst to the west they are 

 faulted down to a great depth under the Trias, which here forms 

 a low flat maritime plain. 



Although it would thus appear that the coal field is compact, 

 yet faulting and denudation have been so extensive that no 

 complete correlation of the coals has yet been established. 

 Whilst also some of the seams are fairly persistent, others thin 



* Mem. Geol. Survey. Geology of country around Oldham and Manchetter, 1864, p. 

 36, Professor Ed. Hull. 



t Hull's Coalfields ol Great Britain, 4th Ed., 1881, p. 197. 



