PRE-CAMBRIAN VOLCANOES 
BOOK 11 
136 
calate with fine felspatliic grits, which distinctly mark the stratification of 
the whole. 
The remarkahly coarse breccia of Benselilfe is mainly made up of blocks 
of quartz-porphyry, felsite or rhyolite, with slate fragments. The Eoecliffe 
agglomerate, another extraordinarily coarse rock, consists of slate fragments 
imbedded in an andesitic matrix, some of the blocks of slate being six 
feet long. The finer tuffs have been ascertained to consist of felsitic or 
andesitic detritus, sometimes forming exceedingly compact flinty rocks or 
hornstonos. 
In this thick accumulation of detrital rocks we are presented with a 
series of alternations of coarser and finer pyroclastic material, interstratificd 
among green, grey and purple slates and grits, which probably represent 
the non-volcanic sediments of the time of eruption. The succession of 
strata bears witness to a long series of eruptions of varying intensity, but 
culminating at two distinct periods in tlie discharge of huge blocks of rock 
('Benselilfe and Eoecliffe agglomerates). 
After some search I have been unable to detect a single vesicular frag- 
ment among the stones in the breccias and tuffs, and Messrs. Hill and 
Bonney were not more successful. Not a trace of anything in the least 
degree scoriaceous is anywhere to be found. Tlie paste in which the blocks 
lie consists of such fine material as would result from the trituration of 
felsite and slate. It contains many broken crystals of felspar, with grains 
of clear quartz. A gradation can be traced from the coarser into the finer 
bands of volcanic and non-volcanic material, fine slates being also inter- 
leaved with highly-felspathic partings of grit. 
Having looked with some care for a trace of a true volcanic neck in 
the district, I have not seen anything that could be unhesitatingly so 
designated. Even in tJie north-western part of the district, where the 
breccias are coarsest, and there is least trace of ordinary sediments, some 
signs of bedding can usually be detected in tlie position of the imbedded 
stones and the partings of finer tuff. Both the coarser and finer detritus 
suggest the kind of material discharged from vents before the uprise of any 
lava. The entire absence of scoriaceous fragments is noteworthy, and the 
abundance of slate blocks rather points to the early eruptions of a volcanic 
focus. Possibly, while the chief centre of eruption lay towards the north- 
west, numerous vents may have been opened all over the district, discharging 
abundant showers of dust and stones, but seldom or never culminating in 
the actual outpouring of lava. 
No indubitable lava-sheet has, in my judgment, been yet recognized in 
Charnwood Forest. A^arious opinions have been expressed as to some of 
the more compact close-grained rocks, and even the verdicts of the same 
observers have varied from time to time, the rocks once considered as felsites 
being afterivards regarded as tuffs, and subsequently placed with the felsites 
or andesites after all. It is not necessary for my present piu’pose to enter 
into these questions, which are rather of local interest. I will only say 
that, in my opinion, the rocks of Sharpley, Peldar, and Bar don Hill are 
