406 MR. BERNARD SMITH O^N THE [Sept. igi2, 



Some of the slates are banded. In such cases it can be shown 

 that the directions of true dip and cleavage-dip are, as a rule, non- 

 coincident and sometimes entirely opposed one to the other. 



The age of these rocks, the nearest equivalents of vrhich are, 

 perhaps, the pale Manx (Barrule) slates, is at present unknown. The 

 slates on the south-eastern side of the tract, which form the floor of 

 the Whicham Valley and the lower slopes on both sides, are of a 

 different type, and should, before long, yield definite palasontological 

 evidence as to their age. They appear to be separated from the pale 

 slates on the west by a plane (perhaps a thrust) which dips in a north- 

 westerly direction at about 15°. They are soft blue shales, ashj-- 

 looking slates, fine black mudstones, and grits. Near Whicham 

 Mill Ford I have found Caryocaris wrightii and an obscure fragment 

 of a graptolite ^ at the quarry west of the mill. 



South-east of the mill the cleavage is disturbed by faults crossing 

 the valley in a north-easterly direction, and on the south side of the 

 valley both dip and cleavage are frequently reversed. 



Upon the north, east, and south-east the slates are bounded by 

 rocks of the Borrowdale Series, from which they are separated 

 either by faults or by thrust-planes. The rocks are chiefl}^ andesitic 

 (and sometimes vesicular) lavas and ashes, many of the latter being 

 coarsely banded. On the north, a well-recognized type is a por- 

 phyritic andesite occurring, with associated ashes and vesicular 

 lavas, between Bootle and Stoneside Hill. On the north-east are 

 the andesite and ashes of Mere Crags, and the banded ashes of 

 Lath Eigg, some of which contain fragments of rhyolite ; and on the 

 southern slope of AY ray slack Hill, about half a mile east of Knott 

 Hill, occurs a coarse breccia, with blocks of spherulitic rhyolite 

 measuring up to 2 feet in length. 



Cleaved and banded ashes also occur between Milloui and The 

 Oreen. 



In addition to the above, there are numerous small intrusions in 

 both Borrowdale rocks and Skiddaw Slates. 



The volcanic rocks are flanked on the south-east, near Millom, 

 by rocks of the Coniston Limestone Series and Carboniferous 

 Limestone. 



About 2 miles north of Black Combe summit the southern part 

 of the Eskdale Granite is in contact with a narrow strip of volcanic 

 rocks aveiaging only half a mile in width. The northern margin 

 of the Skiddaw Slates is, indeed, within the metamorphic aureole 

 of the granite, which makes it difiicult to determine accurately the 

 position and character of the junction between slates and volcanic 

 rocks. The granite averages 2 miles in width as far north as the 

 mouth of Eskdale, after which its outcrop expands considerably. 

 Its eastern boundary forms fairly high ground, but on the west 

 there is a descent to a low plateau dissected by the marginal 

 drainage of the ice-sheet. 



^ Harkness records Graptolites Sagittarius from the debris of quarries in 

 the southern escarpments of the mountain ; see * On the Skiddaw Slate Series ' 

 q,. J. G. S. vol. xix (1863) pp. 131, 132. 



