CHAP. VIII 
CHARNWOOD FOREST 
135 
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 lias suggested that 
they may he still more ancient, and may he regarded as pre-Camhrian. 
The rocks of Charnwood forest have been the subject of an exhaustive 
research by the Eev. E. Hill and Professor P>onney, 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. tV. "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. MTitts has proposed the following classi- 
fication of the rocks : — ' 
7 Groby and Swithland slates. 1 
6. Hanging Hooks conglomerate and - The Brand series. 
Bradgate quartzite. J 
5. Woodhonse beds (ashy grits). 
4. Slate-agglomerate of Roecliffe. The Maplewell series (volcanic 
3. Hornstone beds of Beacon Hill. tuii's and agglomerates). 
2. Felsitic agglomerate of Benscliffe. 
1. Quartzose, felspathio and felsitic grits . The Blackbrook series. 
Under any computation or measurement, the total thickness of detrital 
baaterial in this series of formations must amount to several thousand feet. 
The chief interest centres in the middle series, which consists largely of 
fragmental volcanic rocks, with interailations of slate and grit. As was 
first shown by Mr. Hill and Professor Bonney, these volcanic materials 
vary from exceedingly coarse agglomerates to fine, ashy or felspathic 
slates. lu most cases distinct bedding can be recognized in them, but 
'bore particularly in the fine-grained material. Yet even among the 
massive agglomerates a tendency may be seen tow’ards an orientation of 
the blocks with their long axes parallel. That this arrangement is not 
entirely due to the effects of cleavage may be inferred from the many 
exceptions to it, which would hardly have occurred had such powerful 
cleavage affected the whole district, as would be needed to rearrange the 
large blocks in the agglomerates. Besides, the coarser parts often inter- 
^ Annual Report of Director-General of the Geological Survey, in the Report of Science and 
Art Department for 1895 . 
