262 
CAMBRIAN ROCKS AT DOSTHILL. 
I found at least two varieties of igneous rocks penetrating 
annelidean shales of Cambrian age. There is a line of fault 
on the east, as well as on the west, by which the Cambrian 
and igneous rocks are sharply divided from the coal measures. 
Dostliill lies twelve miles north-east of Birmingham, and 
two miles south of Tamworth. It is close to the Midland 
Railway (Birmingham and Burton branch), lying on the west 
of the line nearly midway between the stations at AYilnecote 
and Kingsbury. The extent of the ridge is one mile from 
north to south, and a quarter of a mile from east to west. 
The River Tame meanders over a plain of Keuper Marls on 
the west side of Dostliill, and the little eminence rises almost 
precipitously from this plain to a height of perhaps 200 feet. 
On the east side the slope is more gentle, though still rapid. 
Attacking Dostliill from the west, we find at the foot of the 
highest and steepest part an exposure of a hard brown grit or 
quartzite; then conies the mass of the ridge, in which exposures 
are not good or frequent. Where the rock is exposed we can 
clearly distinguish (a) a dioritic rock of a dull greenish colour, 
remarkably tough and refractory ; (6) narrow dykes—similar 
to those called “ dun-dykes ” by the Hartshili quarrymen— 
of a brownish colour, very rotten and decomposed ; (c) pale- 
grey shales—precisely similar to certain beds in Merevale 
Park, &c., on the opposite side of the coalfield—traversed by 
innumerable worm-borings, which usually run either parallel 
to the bedding, or at right angles to it. I have found obscure 
traces of other fossils, but the time at my disposal has not 
hitherto allowed me to make any thorough search of the beds. 
All these rocks are very much jointed. The exact simi¬ 
larity of this group of strata, the associated igneous and 
aqueous rocks being precisely alike in their characters, to the 
strata between Atlierstone and Nuneaton on the east side of 
the Warwickshire coalfield, which it was my pleasure to aid 
Professor Lapworth in proving, also in May, 1882, to be of 
Cambrian age, compels us to assign these Dostliill Shales 
also to the Upper Cambrian Period. 
At the southern end of the Dostliill ridge there is a field- 
quarry in which an admirable section is shown of a “ neck ” 
of igneous rock, rising through the Cambrian shales and 
spreading out above and over them. The shales show small 
simis of alteration, and that only in immediate contact 
with the dyke, where their surfaces look burnt, and dis¬ 
coloured by an irony deposit. A stream-course in this 
field runs across the ridge and ought to yield a good section, 
but on the occasions of my visits it has been so overgrowu 
with vegetation as to be impassable. 
