234 TRANSACTIONS OF THE [MAR. 15, 



Fourteen seams are workerl, yielding nominally about 60 feet 

 of coal ; but from this must be deducted the thickness of shale 

 partings, bass and dirt bands which frequently occur. 



The lowest bed of the series is the Arley Mine. 



The Cannel Mine, which occurs some way above it, is remark- 

 able in that it consists of a basal layer of bituminous coal, and 

 an upper layer of cannel which has a thickness of three feet at 

 Wigan and thins away in all directions from it; the common 

 coal thickens as the cannel diminishes. 



The Trencher Bone is of good quality in some parts of the 

 area, whilst in others it contains so much dirt as to prove un- 

 workable. 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 Mill- 

 stone Grit north of Bolton in a southerly direction to Manchester 

 along the line of the valley of the river Irwell ; the downthrow 

 is to the northeast and is over one thousand yards. 



The various seams given on the seciion 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 

 coal field. 



(c) Wigan and St. Helens Area. 



In this area, as in the previous one, the Middle Coal Measures 

 are about one thousand yards in thickness. The St. Helens 

 district forms the most westerly section of the south Lancashire 

 coal field, that of Wigan lying between it and the Bolton area. 



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, alterations in 

 thickness and character of the intervening non-productive meas- 

 ures and the extensive faulting:. 



