Mackhintosh-—Notes on Charnwood Forest. 499 
general conformation to have arisen from an anticlinal elevation by 
which its stratified masses were divided so as to cause those on one 
_ side to dip to the NE. and those on the other to the SW. Some 
have supposed that the upcast to the south-west was very much 
greater than in the opposite direction. 
Syenitic Knolls.—A line of knolls or patches—in some places sye- 
nite, in others greenstone—stretches at intervals from New Cliff and 
. Long Cliff, by Benscliff, towards Bradgate, which Mr. Coleman believed 
to run roughly parallel to the anticlinal line of the forest.* But the 
principal Syenitic bosses are Mount Sorrel to the east, and Mark- 
field Knoll, Cliff Hill, and Stanton Fields to the south-west. Syenite 
may likewise be seen at Hammercliff and Birchwood Plantations, at 
Bardon Castle, Groby, &c. Soni have supposed that these syenitic 
bosses are remaining portions of a great mass or masses erupted pre- 
viously to the deposition of the slates, which, so far as yet observed, 
lie apparently undisturbed in their immediate neighbourhood ; fF 
others believe that the syenites were erupted contemporaneously 
with the slates aud porphyries of which the Forest district is prin- 
cipally composed. Do these syenites mark the craters or centres of 
eruption from which beds of lava overflowed ?—these beds at first 
assuming a syenitic structure, and at a greater distance becoming 
porphyry ? and can the origin of the porphyritic beds of*Charnwood 
Forest be in this way explained ? { Or does the great difference in 
lithological structure between the syenites and porphyries preclude 
this supposition ? At Hammercliff, Mr. Jukes observed an apparent 
transition from syenite to porphyry—the summit and probable 
nucleus of the hill being syenite, with a surrounding porphyritic 
mantle. But might not these phenomena be regarded as equally in- 
dicative of the syenite having been thrown up since the formation of 
the porphyry so as to elevate the latter ail around it, and at the same 
time obliterate the line of junction by metamorphism? Bardon Hill, 
to the west of Hammercliff, appears to be greenstone at the top, 
with a porphyritic structure lower down, which Mr. Hull regards as 
a passage between the greenstone and the porpliyritic ridges to the 
north—the two having been separated by a fault. But might not this 
fact be likewise regarded as a proof that Bardon Hill was elevated 
after the formation of the porphyry? In the neighbourhood of 
Bardon Hill, and resting unconformably on the Coal-measures, is a 
sheet of greenstone quite distinct from porphyry in its composition, 
and in many places differing but little from compact basalt ; speci- 
mens of it may be seen near the office of the Whitwick Collieries.§ 
* Had these igneous rocks anything to do with the anticlinal upthrow, which 
Mr. Hull and others believe to haye occurred at the close of the Carboniferous 
period, or are they of much older date ? 
+ Too much importance cannot be attached to the examination of fresh excayva- 
tions in the quarries of Markfield Knoll, Groby, &c., in order to discover, if possi- 
ble, the actual contact of the igneous and sedimentary rocks. 
+ See Prof. Ramsay on North Wales, in the first volume of ‘The Geologist.’ 
§ In one of the neighbouring Snibston pits it was found to be 21 feet in thick- 
ness. In two of the Whitwick shafts its thickness is 63 feet. 
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