_ 600 Mackintosh—Notes on Charnwood Forest. 
Can this flow of trap be traced to Bardon Hill ? or (according to a 
local geologist) to a greenstone-rock near Whitwick ? oz to neither ? 
Porphyritic Rocks.—These rocks may be seen exposed at intervals 
along the irregular ridge extending from Grace-Dieu to Green Hill. 
The rocky projections called High Cademan, High Sharpley, Rachet 
Hill, Pedlar or Peldar Tor, High Towers [Tors?], Timberwood 
Rocks, Flatfield Rocks, the Hanging Stones, &c. are more or less 
composed of porphyry; these tors, taken as a whole, present a 
wonderfully uniform porphyritic structure, as may be seen in the 
stones of which the roadside walls near Whitwick have been built. 
But as the geologist proceeds with his hammer to examine the rocks 
of the different tors he now and then finds unexpected variations in 
their composition, graduating frorf felspar, and compact felspathic 
porphyry, through the ordinary varieties, to porphyritic and compact 
greenstone. He.may in some places see the porphyry covered or 
underlain by what Mr. Hull calls ‘slaty ash.’ That gentleman has 
observed a bed of altered slate in the interior of the Forest, ap- 
parently dipping under the porphyry. This would seem to indicate 
that the overlying bed or beds of porphyry must have flowed over 
the slate from a submarine volcanic vent. On ascending from the 
Hanging Stones to the High Towers, I have noticed some striking 
variations ifithe composition of the rocks. At the Hanging Stones, 
a brecciated structure is combined with a porphyritic. Ata high 
level, between Mr. Green’s house and the lodge, the rock is a very 
coarse breceia, which, if not directly volcanic, must have been highly 
metamorphosed ; higher up the structure becomes more decidedly 
porphyritic. On this acclivity groups of rocks, reminding one of 
what may often be seen on sea-coasts, may be traced at different 
levels, with intervening flat areas which may have been sea-beaches 
during the last emergence of the Forest district. 
On the side of the foot-path leading from the Reformatory road 
towards Green Hill, I noticed a block of porphyry enclosing a frag- 
ment of tine slate, with the boundary line between the two very dis- 
tinctly marked. Many similar instances have been discovered ; and 
how far these included fragments furnish evidence of the porphyry 
of the district having once been in a molten state, is a very important 
inquiry in the present state of geological speculation. Mr. Coleman, 
an advocate for the metamorphic origin of the Charnwood por- 
phyries, admitted that there must have been fusion at those places 
where the slaty fragments were caught up; but why, it may be 
asked, have recourse to this explanation in the case of particular 
phenomena, and deny the volcanic origin of the rocks in general? 
The advocate of metamorphism might reply that the doctrine of 
‘easier fusibility’ is implied in the very fact of unaltered or little 
altered fragments of slate occurring in the porphyry ; and that the 
latter therefore, generally speaking, may be of metamorphic origin, 
though in parts it may have been ‘heated to the melting point.’ In 
this district the respective claims of the rival theories—metamorphism 
and igneous fusion—may be studied within a very limited area. The 
observer ought previously to be well acquainted with the results of 
