604 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [June 22 
predominating. These beds form the whole of Brackenriggs Fell as 
far as Shoulthwaite Gill, They vary much in character, being 
sometimes compact and fine-grained, at other times highly porphy- 
ritic. In places the bedding is well shown, the dip being 8.8.E. at 
25° to 30°. At Shoulthwaite a synclinal fold occurs ; and in proceed- 
ing up Shoulthwaite Gill we have a repetition of these bedded traps, 
with a few ashy and brecciated beds, the sheets of trap dipping 
northwards at angles of from 20° to 30°. This northerly inclination 
is particularly well exhibited in the flanks of the Benn and Low 
Bank, on the eastern side of the valley, and of Castlerigg Fell and 
Bleabery Fell, on the western side. 
IV. Lower portion of the Green-slate Series in the Vale of St. John. 
The north and south ridge which separates the valleys of Naddle 
Beck and the vale of St. John, exhibits a very clear section of the 
lower portion of the Green-slate series (fig. 3). The extreme northern 
end of this ridge, known as Low Rigg, is entirely composed of the 
intrusive syenite which I have described as occupying the mouth of 
the vale of St. John (Quart. Journ. Geol. Soc. vol. xxv. p. 435). 
Southwards the syenite is succeeded at the Chapel of St. John by a 
compact, fine-grained, dark-green, felspathic trap, which forms the 
northern end of Naddle Fell, and is well seen above the farm of 
Rake How. This trap is the lowest member of the Green-slate 
series ; and it forms a tabular mass of considerable thickness, which 
dips 8.8.E. at about 30°. It is not, however, succeeded by ashes 
and breccias, as in Borrowdale and at Keswick ; but itis overlain by 
a great series of felspathic traps and greenstones, which form the 
whole of Naddle Fell and High Rigg, on the western side of the Vale 
of St. John. Occasionally there occur thin bands of ash, as at Sos- 
gill and Low Bridge End; and at this latter place the ash is highly 
amygdaloidal. This succession of bedded traps is exceedingly well 
displayed along the flanks of Naddle Fell, forming a series of oblique 
terraces, which dip 8.8.E. at about 30°; and a similar sequence of 
beds, though not in so marked a form, appears to obtain in Wan- 
thwaite Crag, on the eastern side of the valley. The traps of Naddle 
Fell vary a good deal in lithological characters, being usually more 
or less porphyritic and containing a considerable quantity of horn- 
blende. At the southern end of Naddle Fell there is a highly por- 
phyritic trap, which closely resembles some of the beds seen near 
Aira Force; and this is overlain in Warren Crag by a great mass of 
greenstone, which seems to be a continuation of the celebrated Castle 
Crag, on the eastern side of the valley. If this is the case, however, 
it is shifted to the north by a fault. The whole series of traps is 
succeeded close to Smeathwaite Bridge by bedded felspathic ashes, 
which dip §.8.E. at 45°. Continuing the section from Smeathwaite 
Bridge down the western side of Thirlmere, we cross again a similar 
series of traps and greenstones to those which occur in the Vale of 
St. John, the repetition being doubtless due to the occurrence of a 
synclinal, though it is extremely difficult to make out any dips. 
