DIORITES OF THE WARWICKSHIRE COAL=FIELD. 637 
47. On the Drorirus of the WARWICKSHIRE CoAL-FIELD. 
By 8. Attrorr, Esq., F.G.8. (Read June 25, 1879.) 
In a paper communicated to the Geological Society, and published 
in the 30th volume of the ‘ Quarterly Journal,’ I briefly described the 
microscopical structure and composition of the various masses of 
igneous rocks which occur in the Carboniferous strata of the Midland 
Counties, with the exception of those found in the Warwickshire 
Coal-field. I now propose to complete the series with a short 
account of the only hornblendic rocks to be found among them. 
Although they form but a small group they are of considerable 
interest, as some of them present remarkable varieties of structure, 
and others a mineral constitution which distinguishes them from 
any British rocks hitherto examined. 
The geology of the Warwickshire Coal-field has been described 
in the Memoir of the Survey published in explanation of sheet 
lxiii. 8.W.; and a reference to that map will show that the rocks 
now to be described are restricted to the district between Atherstone 
and the village of Marston Jabet, about two miles south of Nuneaton, 
and also that the several bands and larger masses occur only in the 
lower unproductive beds of the Coal-measures and in the underlying 
Millstone Grit. Although the sheets usually run very regularly 
between the beds of shale they are clearly intrusive, as they some- 
times pass from lower to higher beds, and have invariably altered 
the shales in contact with their upper and under surfaces. The 
junction of the eruptive and sedimentary rocks may be seen in 
several clear sections. Ina quarry in Purley Park, about a mile 
south of Atherstone, there is a good exposure of both rocks ; at first 
sight they appear to be interbedded, but in one place there is a 
wedge-shaped band of shale enclosed in one of the sheets of trap. 
A still more interesting example may be seen in the railway-cutting 
near Chilvers Coton, where there are no less than ten alternations of 
the two rocks (see fig.). Although the geological period of the 
Diorite intrusive in Carboniferous Shales in Railway-cutting near 
Chilvers Coton. 
a. Shales. 6. Diorite. 
Q. er, 8. No. 140. 2x 
