The truly volcanic nature of these remarkable rocks was first pointed out by Mr. S. Allport, F.G.S., and their original characteristics, and the changes they have undergone since their formation, have been described by him in a well-known series of memoirs. Their geological position, and their relation to the associated fossiliferous strata, and to the similar rhyolitic rocks of Caer Caradoc and Pontesbury have been fully discussed by Dr. C. Callaway, F.G.S. (_c._) NUNEATON (CALDECOTE HILL).--A thin group of volcanic breccias and tuffs, with associated quartz-felsites, and diabase, rises out from below the Upper Cambrians of Nuneaton, in the Park of Caldecote Hill. The lowest zone of the overlying Cambrian Hartshill quartzite is in part composed of their fragments. The ashes are shewn in old cuttings to the north-west of Caldecote Lodge, the quartz-porphyries and diabase in an old quarry about a quarter of a mile to the southward, while the breccia composed of the fragments of these old rocks, in the base of the Cambrian quartzite is best shewn on the tramway still farther to the southward, leading down to the Coventry Canal. (_d._) CHARNWOOD FOREST.--This district is formed of an island of ancient igneous and stratified rocks rising out from below the Upper Trias. The stratified rocks are almost wholly composed of materials of volcanic origin, and shade off on the one hand into coarse volcanic agglomerates, and on the other into fine green slates like those of the Borrowdale series in the Lake District, to which indeed the whole of the bedded Charnwood rocks bear a striking resemblance. The stratified volcanic rocks are pierced by numerous igneous intrusions. The most conspicuous are those classed by Professor Bonney, F.R.S., as syenite. These are most conspicuous near Groby, Bradgate, and generally in the south eastern parts of the Charnwood area. A mass of beautiful hornblendic granite rises through the Trias immediately to the east of Charnwood Forest at Mount Sorrel, near Barrow on Soar. A few later dykes of altered andesite occur within the forest itself, and diorite in the outlier of Brazil Wood. To the south of Charnwood Forest, several remarkable points of syenitic rock protrude through the flat-lying Trias. The most conspicuous of these are the hills of Sapcote, Croft, and Enderby. There is no direct evidence of the Cambrian or pre-Cambrian age of the Charnwood rocks, but strata identical with the fossiliferous Stockingford shales (Upper Cambrian) of Nuneaton, have been pierced in several borings through the Trias near Leicester, Market Bosworth, etc., and appear to rest at once upon the Charnwood rocks, as do the Nuneaton beds upon the Caldecote volcanic group. CAMBRIAN ROCKS.