60 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [DeC. 3, 



Fell, the upper part of which is composed of nearly horizontal beds 

 of the Scar-limestone, under which are seen the great undulating 

 masses of Horton flagstone. It is obvious, at first sight, that the 

 flagstone must have been elevated, contorted, and solidified ; and 

 afterwards planed down by denudation, until, throughout wide spaces, 

 it presented at the bottom of the sea a series of nearly dead levels, on 

 which were gradually accumulated the great reefs and shell-beds of 

 the Scar-limestone. 



The base of the Scar-limestone at the S.E. end of Moughton Fell 

 is so far above the level of the corresponding base-line immediately 

 above Horton, that we may suspect the existence of a fault down the 

 valley of the Ribble ; or the change of level may perhaps arise from 

 the natural dip of the limestone in the neighbouring district. The 

 line of section does not show the immediate relations of the group last 

 described {d) to the Horton flagstone (c) ; but we are not left in doubt, 

 for the calcareous slate-group at the foot of Penygent is (on the left 

 bank of the Ribble) overlaid by the flagstone-series, in which there 

 is a prevailing southern dip, which is continued nearly two miles 

 down the valley below Horton. The Studfield flag-quarries (fig. 5) 

 are in this part of the series ; and they may be connected, through 

 quarries opened in Dry-rigg, with the flagstones of Moughton Fell. 

 In this way we obtain a proof that the group of Moughton Fell im- 

 mediately overlies the calcareous slates {d) at the foot of Penygent. 



The Horton flagstone has none of the chloritic colour which 

 distinguishes the lower group, and in this respect it resembles the 

 Coniston flagstone, to which it ofl*ers many near analogies. It is, 

 however, connected physically, through the alternations of hard beds 

 of grey calliard, with the lower group ; and it is not, I believe, possible 

 to define the exact line between them where they exist in continuity. 

 The flagstones follow the laminations of deposit, are of excellent 

 quality, and may be obtained of enormous size. Generally, except 

 where they pass into the condition of a grit, they show cleavage- 

 planes, which sometimes (though rarely) produce a striation on the 

 surfaces of the flags and injure their quality ; but no slates are ob- 

 tained from these cleavage-planes. 



I do not wish to describe in much detail a group that has been well 

 described by Professor Phillips ; but the following short notes, made 

 on the spot, may be worth recording, as they give the evidence for 

 some of the flexures delineated on the accompanying section, fig. 6. 



1 . Crossing from Horton to the northern flag-quarry of Moughton 

 Fell, we first traversed a series of coarse slates and hard grey grits 

 {calliards of the quarrymen) dipping nearly south. At the quarry 

 the great flagstone dipped 20° W. of Mag. S. Z 42°. Many of these 

 beds were marked by a cleavage-plane striking 40° E. of Mag. South, 

 and dipping at an angle of more than 80°, to a point 40° S. of Mag. 

 W. At a short distance the dip of the flags was 30° W. of Mag. S. 

 Z 50° ; and here were cleavage -planes inclined at about 35° to the 

 planes of stratification. So far as was observed, there did not seem 

 to be much constancy either in the strike or inclination of these 

 cleavage-planes, and the quarrymen turn them to no use, the flags 



