1870.] NICHOLSON—LOWER GREEN SLATES AND PORPHYRIES. 609 
stone. Above this point the stream cuts, for about a quarter of 
a mile, through glacial drift containing many blocks of trap and 
pieces of Skiddaw Slate. Here a little stream flows into the Lowther 
from the west, and exhibits the Skiddaw Slates a good deal contorted, 
but dipping on the whole 8.S.E. These are almost immediately 
succeeded by a greenish-grey fine-grained felspathic trap, which 
forms the base of the Green-slate series. This is sometimes slightly 
hornblendic, and with some coarse ashy-looking beds occupies the 
ground up to the mouth of Keld Beck, also flowing into the Lowther 
from the west. Nearly half a mile to the south-east of Keld Beck 
is a third tributary, called Thornship Beck; but the ground between 
these two streams is moory, and exhibits only a few scattered bosses 
of trap. In Thornship Beck, at its head, are seen bedded felspathic 
ashes, sometimes purple, sometimes green, with veins of quartz, and 
nodules of bright red jasper, and haying intercalated amongst them 
one or two beds of trap. In the lower part of Thornship Beck the 
Skiddaw Slates again come on, and have been worked for slate- 
pencils. Their appearance here would appear to be most probably 
due to faulting, the dip varying a good deal; but at the quarries 
there is a small anticlinal. The country to the south-west of Thorn- 
ship Beck is very moory, and no rocks are seen im situ except a 
small exposure of a greenish-grey felspathic trap at the mouth of 
Thornship Beck. The termination upwards of the Skiddaw Slates 
is therefore not seen. The next exposure of rock is at a farm- 
house called Kemp-how, situated on the Lowther, about half a mile 
to the south-west of Thornship Beck. Between this point and 
Cragg’s Mill there is a fine section of some of the lower beds of 
the Green-slate series, consisting entirely of ashes and breccias, 
all highly cleaved. Some of the ash-beds have the ordinary cha- 
racters of the “green slates;” others are breccias, in which the 
included fragments consist entirely of ash; and others are amyg- 
daloidal, containing numerous sinuous vesicles, which are either 
empty or filled with quartz. The strike of the beds is a good 
deal deranged, varying from 8.8.W. and N.N.E., through E.N.E. 
and W.S.W., to nearly due W. and E., the cleavage throughout 
being nearly vertical. 
From the position of these beds there can be no doubt of their 
being the equivalent of the great slate-band of Honister and Bor- 
rowdale ; and they thus afford a useful guide in mapping this region. 
They can be traced to the south-west along the northern side of Wet 
Sleddale, through the higher part of Swindale, across the head of 
Long Sleddale (in the Gatesgarth Pass), across Kentmere (near the 
Reservoir), and across the head of Troutbeck; and I have little doubt 
of their identity with the great band of slates which is worked 
between Rydal and Grasmere, and again still further to the south- 
west in Tilberthwaite, and in the Dunnerdale Fells. In all these 
localities I believe that these slates point to an horizon very close to 
the base of the whole series of the Green Slates and Porphyries, 
though not far removed from the southern limits of the great area 
oceupied by this formation. 
