FOUND IN THE LANCASHIRE COAL FIELD. 117 



last locality the contents of the joints bear every appear- 

 ance of having been precipitated from an aqueous solution 

 on the sides of the fissure, there being no traces of disloca- 

 tion of the strata, nor any alteration in the nature of the 

 rock enclosing them. Crystals of sulphuret of lead, and 

 more rarely also of sulphuret of zinc, are met with in the 

 hollows of nodules of ironstone, and clearly show that they 

 have been separated from the matrix in which they are now 

 imbedded, when it was in a pasty state. Indeed there is 

 now little doubt but that the contents of metallic veins may 

 be classed under three heads ; namely — those injected from 

 below into the fissures of a rock ; those which have been 

 infiltrated from above into fissures, and those veins and 

 detached crystals which have separated themselves from the 

 mass in which they are now imbedded when it was in a 

 semi-fluid state. 



The greater portion of the South Lancashire coal field, 

 west of a line from Manchester to Fenniscowles, near Black- 

 burn, is surrounded on three of its sides by members of the 

 upper new red sandstone formation.* On the southern part 

 of the field, the upper coal measures dip under the sandstone 

 towards the south. On the north side, the millstone grits, on 

 their rise, abut against the sandstone, and dip to the south- 

 west; and on the west, the lower coals do the same, dipping 

 eastwards. On the west side of the coal field are several hills 

 of considerable height, such as Harrock Hill on the north, 

 Parbold HiU, Ashhurst Beacon, and Billinge Beacon, on the 

 west; points which are seen as prominent objects on enter- 

 ing the estuary of the Mersey from the sea. The forces 

 which elevated the coal measures appear to have gone from 

 the moorland district east of Chorley, in a W.S.W. direction 

 to Harrock Hill, and then suddenly turned south to Knows- 

 ley and Huy ton. On the west side, below Ashhurst Beacon, 



* See Map of the Lancashire coal field, by James Heywood, Esq., M.P., 

 F.R,S,, published in vol. vi. p. 426 of the Society's Memoirs. (New Series.) 



