To these vestiges of an early Mesozoic land, still half buried among Triassic strata, a peculiar interest attaches from the obviously high antiquity of their rocks and their uprise in the very centre of the island. Various opinions have been expressed as to the age of their component rocks. When they were mapped by the Geological Survey they were recognized to be as old as any group of rocks then known, and they were accordingly placed in the Cambrian system. More recent research has suggested that they may be still more ancient, and may be regarded as pre-Cambrian. The rocks of Charnwood Forest have been the subject of an exhaustive research by the Rev. E. Hill and Professor Bonney, to whom most of our knowledge regarding them is due. These observers first pointed out the truly volcanic nature of the coarse clastic rocks of the district. They have traced their relations in the field, and have likewise described their structure and composition as shown by the microscope. Subsequently the district has been re-mapped on the scale of six inches to a mile by Mr. Fox Strangways for the Geological Survey, while Mr. W. W. Watts, another member of the Survey, has studied the petrography of the ground, and has traced the boundaries of the several rock-groups so far as these can be determined. Confirming generally the stratigraphical arrangement sketched by Messrs. Hill and Bonney, Mr. Watts has proposed the following classification of the rocks:--[78] 7. Groby and Swithland slates. } } 6. Hanging Rocks conglomerate and } The Brand series. Bradgate quartzite. } 5. Woodhouse beds (ashy grits). } } 4. Slate-agglomerate of Roecliffe. } The Maplewell series (volcanic } tuffs and agglomerates). 3. Hornstone beds of Beacon Hill. } } 2. Felsitic agglomerate of Benscliffe. } 1. Quartzose, felspathic and felsitic grits. The Blackbrook series. [Footnote 78: Annual Report of Director-General of the Geological Survey, in the _Report of Science and Art Department for 1895_.]