GEOLOGY sist of sheets of volcanic breccia, tuffs, and volcanic grits, with a few intrusive dykes of basic rock. The lowest beds of the series are some coarse breccias met with in a disused road near the Anchor Inn. The more compact tuffs with the aspect of brecciated quartz-felsites are exposed in Mr. Abel's Long Quarry immediately south of Hartshill Grange, and remarkably fine- grained tuffs are to be seen in the sides of an old tunnel 100 yards west of Caldecote Hill House, where, according to Mr. Strahan, the bedding planes dip at 25 to 30 in the same direction as those of the overlying quartzite, that is, about south-west. An intrusive basic rock, a porphyritic basalt according to Professor Watts, 1 takes the form of a dyke which intrudes upon and partly over- lies the ashes, and is exposed in an old paving-cube quarry known as the Blue Hole, about a quarter of a mile east of Caldecote Windmill. The rock into which it intrudes has the appearance of a quartz-porphyry, but Professor Watts, who describes it as the ' quartz-felspar rock,' is inclined to regard it as a tuff.* A similar and possibly the same dyke of porphyritic basalt traverses the ' quartz-felspar rock ' at the entrance to Mr. Abel's quarry near Hartshill Grange. Professor Lapworth is of opinion that the Caldecote rocks are theoretically paralleled with the Upper Longmyndian and Uriconian groups of Shropshire. 3 From the foregoing details it will be seen that the earliest and lowest Warwickshire deposits were produced by the agency of volcanoes. Exactly where these were situated it is as yet impossible to say, but in the Charnwood district, a few miles to the north-east, there are con- siderable masses of somewhat similar volcanic materials, though it is thought that these are of an earlier date ; here, according to Professor Bonney, we have the site of a volcanic cone or group of cones which threw out dust and fragmentary materials into adjacent shallow lakes or lagoons. 4 It seems likely that at this time the area which is now Britain was occupied by an archipelago of small volcanic islands. Such conditions were not perhaps highly favourable to the existence of living beings in the surrounding waters ; nevertheless life was not entirely absent, for a few fossil worm-burrows have been discovered in some of the Charnwood rocks, though none has yet been met with in the Caldecote beds. CAMBRIAN After a while this low-lying tract of volcanic islands subsided beneath the waters and was in part covered by several thousand feet of Cambrian sands and muds. These, the lowest rocks in which fossils occur in any abundance, are found to overlie the Archaean rocks in the 1 Pnc. Geol. AIIOC. xv. (1898), 391.
- Watts, op. cit. p. 392. See also Rutley, Geol. Mag. (1886), p. 557 ; and Waller, ibid. p. 322.
8 Lapworth, Pnc. Geol. dsioc. xv. (1898), 327.
- A. J. Jukes-Browne, The Building of the British Isles, ed. 2 (1892), pp. 29-32.
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