70 
PRE-CARBONIFEIiOUS FLOOR OF THE MIDLANDS 
hand, bat gradually sloping to the higher surface of the 
Warwickshire coal-field which lies to the west and south. 
The altitude of the ridge is about 500ft., and from the road 
which runs along the crest the view extends to the blue hills 
of Cliarnwood, fifteen miles away, and westward—across the 
* 
coal-field—to the bossy mass of Dost Hill. Examining the 
very base of the Hartshill Range, rocks of Pre-Cambrian age 
can be detected near the windmill at Caldecote. Here, in a 
little spinney between the mill and a large house, there is an 
old disused quarry in which a good section is exposed. The 
bulk of the rock is a dark basaltic-looking mass—possibly a 
diabase—which breaks across a very interesting rock—a 
quartz-felsite*—of which only a small portion is visible at 
the northern end of the quarry. This quartz-felsite nmeli_ 
resembles similar rocks which occur in the Pre-Cambrian 
formation near Llanberis in North Wales. Below these rocks, 
in a kind of tunnel leading towards the house, we find volcanic 
grits and ashes comparable with those which are so common 
in Cliarnwood Forest. Altogether the Pre-Cambrians here 
form a narrow strip rather more than a mile in length, bounded 
to the east by a fault whose throw must be very great, since 
it brings the Keuper marls to a level with the Arcluean strata. 
The Quartzite of Hartshill .—Resting upon the volcanic 
rocks just described we find a considerable thickness of a 
metamorphosed sedimentary rock—a quartzite (once a sand¬ 
stone) about 1,000 feet in thickness. Its base is a breccia, 
composed of small pebbles of the underlying rocks, but 
higher up it becomes exceedingly hard and compact. In the 
upper portion narrow bands of shale appear, which increase 
in number and thickness towards the top. The strike of the 
quartzite strictly accords with the direction of the ridge 
which is composed of it, being from north-west to south-east 
(parallel to the Cliarnwood axis), while the dip is to the south¬ 
west at an average angle of 35 degrees. The rock is 
extensively worked for road-metal, and is exposed in the 
quarries in a series of magnificent sections, all the way from 
Nuneaton to Hartshill. Its colour varies from white to red ; 
although fossils have been diligently searched for, not a 
trace of one has as yet been discovered. Two dykes of dioritc 
traverse the quartzite nearly parallel to its strike. One is 
well seen on either side of the Midland Station at Nuneaton; 
the other, which is much thinner, is exposed in the quarries 
close to Hartshill. The geological age of the quartzite is a 
* Mr. T. II. Waller has kindly promised to examine these rocks 
microscopically, and to report upon them in an early number of the 
Midland Naturalist. 
