252 A HISTORY OF LONGRIDGE. [Chap. 12. 



and wliose roofs are studded witli many a crystalline pendant and 

 supported by many a huge pillar, which sparkle and glitter in the light 

 of the explorer's torch. There, also, we may revel in lovely dales, 

 the haunt of many a botanical rarity, and carpeted with a short, 

 sweet, green pasture, sure evidence of the fertility of the soil resulting 

 from the denudation of the surrounding rocks. 



The Mountain Limestone abounds in economic products. In 

 Derbyshire it yields our principal lead ore and the fluor-spar with 

 which our pottery is glazed. In other localities it yields lead and iron 

 ores and barytes. It is abundantly used for building purposes, for 

 lime-making, and for road-mending. Many of the so-caUed 

 " marbles " of commerce used for chimney-pieces and other ornamental 

 purposes are fossiliferous Mountain Limestone. 



THE YOEEDALE SERIES. 



Overlying the Carboniferous Limestone we find a series of shales 

 and grits, with thin bands of impure Hmestone and thinner bands of 

 coal. 



These beds were named the Yoredale Rocks by Prof. Phillips 

 because of their development at Yoredale, in Yorkshire. 



In Lancashire these rocks attain their maximum development of 

 about four thousand feet. 



It is a matter of some difficulty to give a satisfactory account of the 

 physical conditions obtaining during the deposition of these rocks. 

 Prof. Green says : — " The mixed deposits of sandstone, shale, and 

 impm-e limestone, which had at first been confined to the neighbour- 

 hood of the shore, now extended over nearly the whole marine tract, 

 and the deposition of the Yoredale Rocks began. At the same time a 

 slow sinking of the sea-bottom set in, which allowed of these beds 

 being piled one on the top of another to a considerable thickness." 

 Further, he allows that there must have been periods of rest or 

 perhaps of slight upheaval. 



Probably, in addition to the above, and in further explanation of the 

 presence of the limestones and coal-seams, there were local areas not 

 undergoing continued subsidence. During the periods of rest, shale 

 and grit were laid down, the sea in these areas became gradually 



