THE GEOLOGY OF PLYMOUTH. 
461 
Slates, limestones, shales, grits, ash beds, and sandstones alternate 
with each other in very remarkable fashion, while faults and con- 
tortions by no means simplify the riddle. Mr. Jukes hints that 
these rocks — their prevalent southerly dip notwithstanding; for in 
dip and strike they follow the general rule of the district — may be 
really under and not over the limestones, brought up by an in- 
verted anticlinal. He seems to have been chiefly led to this by 
the similarity of the rocks between Batten and Eovisand to some 
Carboniferous rocks of Ireland. But this is only a suggestion ; 
and while this third division appears to be cut off on the west 
between Millbrook and Tregantle, on the east its rocks certainly 
extend to Torbay. Dr. Holl points out the strong family likeness 
between our own upper rocks and the succession of rocks on the 
Dart ; and I have traced some of the most characteristic of the 
Staddon beds occupying much the same relative position towards 
the Yealmpton limestone that they do towards the Plymouth. 
I give the descriptions of this group by Sedgwick and Murchison 
and Professor Phillips with my own notes. 
Sedgwick & Murchison. 
Brown and yellow earthy 
slate, with pyritous stains 
and iron veins, some of 
which run in the form of 
strings nearly north and 
south. This mass alter- 
nates three times with 
beds of impure limestone, 
and the last bed occurs 
at Dunstone Point, where 
it thins out to an edge 
among the impure earthy 
slates. This part of the 
section may be considered 
as forming a kind of pas- 
sage from the limestone 
to the super-incumbent 
beds. 
Phtllips. 
Near Turnchapel red 
shales, yellow ochry beds, 
and purple masses of oxide 
of iron, form a parting in 
the limestone, and have a 
varying dip of about 70° 
to the south. 
Laminated schistose 
beds, irregular beds of 
trappean rock with ir- 
regular and nodular ad- 
mixtures of limestone, 
occupy the shore for 
some distance. 
Remarks. 
Some of the trap is 
schistose (? ash), yellow, 
with ochry spots as if 
the result of decompo- 
sition. 
One of the ochry beds 
contains Petraise. 
Some of the beds are 
largely intersected by 
quartz veins, which stand 
out like a network, the 
rock between being wea- 
thered away. 
About midway a fault 
is observable, associated 
with a couple of minor 
faults. Here the dips 
and their directions vary 
from S. 20 E., 35° to E. 
25°, and round to S.E. 
again. The slate which 
succeeds is dark and hard, 
less cleaved, and more 
jointed than usual. 
VOL. VI. 
2 H 
