GEOLOGY Great intrusions of igneous rock took place at various periods in this area. The earliest of these appears to be the porphyroids of Peldar, Sharpley, and Bardon. Following this comes the syenite of Bradgate, Groby, Mark- field, Sapcote, Croft, Enderby and Narborough, that at the four latter localities issuing from under the Trias. Subsequent to this the hornblendic granite of Mountsorrel, Buddon Wood, and Brazil Wood appears to have been intruded, and in these there are dolerite dikes of still later age. The Charnwood Hills are notably dislocated and shattered. The general structure of the district is that of an elongated semidome having its major axis in a north-westerly and south-easterly direction. This axis is a line of fracture, and east and west of it are other faults which repeat the beds, showing that the sides of the arch have been thrust over its centre. Cross faults help to complicate the structure and show the enormous disturbance to which the region has been exposed. That the pre-Cambrian era was one of great volcanic activity is evident from the nature of the rocks, and the intense disturbance of the stratification. It may also be inferred that during this period this part of Britain formed a land surface on which numerous volcanoes were established, and from which vast flows of lava were poured out, and large quantities of volcanic detritus were ejected. Portions of this land sank beneath the sea, in which the denuded material from these volcanic products was spread out in more or less stratified beds. At this period the earth's crust was comparatively thin, and consequently was being continually broken up and crushed by the explosive forces of the contained igneous matter, and by the contraction of the earth's mass as it cooled. This explains the enormous amount of pressure that is evinced in the faulting and overthrusting of these rocks. After the deposi- tion of the pre-Cambrian rocks a great break takes place in the geological succession in this region. No representative of the Cambrian, Silurian, or Old Red Sandstone has as yet been found within the area of the county. While these rocks were being laid down in other districts this part of England appears to have been dry land, although some of these rocks may eventually be discovered beneath the older rocks abutting against the Charnwood Hills or the thick Triassic covering to the east. CARBONIFEROUS CARBONIFEROUS LIMESTONE The Carboniferous Limestone succeeds the pre-Cambrian Rocks, and is found resting against them on the northern side of the range at Grace Dieu. To the north of this it comes to the surface in a series of inliers at Osga- thorpe, Barrow Hill, Breedon Cloud, and Breedon, being turned up against a fault ranging in this direction. It also crops out in the valley at Dimmins- dale, and at Calke and Ticknall in the next county. The limestone has been worked in former times at all of these places, but the only quarries now in use are at Breedon and Breedon Cloud. It is a magnesian limestone or dolomite, and consists of a light-coloured, brownish grey, semi-crystalline rock, which is very hard and full of joints. At the south end, in the neighbourhood of the Charnwood rocks, the lime- stone is browner and more impure, and contains a line of cavities that are 5
