CHAP. VIII 
CHARNWOOD FOREST 
137 
massive rocks, as they have finally been classed by Messrs. Hill and Bonney. 
But I cannot look upon them as lavas, at least I have seen no evidence to 
lead me to believe that they were ever erupted at the surface. I have fully 
considered the arguments of Mr. Hill and Professor Bonney on this point.^ 
There can, I think, be no doubt of the close association of these I'elsitio 
rocks and the breccias, but the structure of the rocks in the field seems to 
me to be decidedly in favour of the view expressed above. The microscope 
affords no assistance in the question.^ The doubtful rocks seem to me rather 
to be intrusive masses which have been protruded into the volcanic sedi- 
mentary series among which they rise. They are acid, fine-grained, poqihyritie 
rocks, wliich would formerly have been included under the general name of 
felsites or quartz-porphyries. Their coarse porphyritic parts rapidly pass 
into close-grained felsitic material. Many of the blocks in the breccias 
are precisely like parts of these rocks. It might hence be asserted 
that tliese fragmental deposits are later than the eruptive bosses. At 
least it is obvious that rocks of the same type as those of Sharpley, 
Beldar, and Bardon Hill must have been disrupted to produce the coarse 
breccias. 
Later eruptive rocks, consisting of masses of syenite and granite, with 
still younger dykes of dolerite, andesite, diorite and felsite, liave successively 
made their appearance, and add to the diversity of the igneous phenomena 
of this district. 
The question of the age of this isolated volcanic series is one of much 
interest, but of great perplexity. Though a resemblance may be admitted 
to exist between some of the slates and parts of the Cambrian system of 
N’orth Wales, the difference between the Charnwood rocks and the un- 
doubted Cambrian series of Warwickshire, only thirteen miles to the south- 
west, is such as to indicate that the former are probably older than the 
latter. While the Charnwood rocks have been intensely cleaved and 
crushed, those of "Warwickshire have undergone no such change. The 
^'I’gillaceous strata in the one region have been converted into slates, in the 
other they remain mere shales. Though cleavage is sometimes irregularly 
developed, its rapid disappearance in so short a distance as the interval 
between Charnwood Forest and Huneaton seems most explicable if we 
suppose that the rocks at the more easterly locality were cleaved before 
those towards the west were deposited. If this inference lie well grounded 
the pre-Cambrian age of the Charnwood volcanoes would be established. 
Hut the argument is not conclusive. No fossils of any kind have yet been 
found in any of the old rocks of Charnwood.® Merely lithological resem- 
blances or differences are all that can be used as a guide to the geological 
'ige of these masses. Mr. Watts has suggested that possibly the quartzite 
^ QmH. Jvurn. Gcol. Soc. xlvii. (1891), pp. 80-88. 
" See ilessrs. Hill and Bonney, op. cit. xxxiv. (1878), p. 211. 
Since this page was in type, Professor Lapworth has found a worm-burrow loiv down in the 
land Series, and one or two additional examples have since been obtained by Mr. J. Rhodes of 
■ t le Geological Survey. These are the first undoubted organisms from the Charnwood Forest 
rocks. Mr. Watts, Gcol. Mag. 1896, ji. 487. 
