Ix 
During the present year Mr. John Arthur Phillips—whose 
researches as a scientific miner do honour to Cornwall—has 
submitted the slates of Polgooth, Polmear, Dolcoath, Botallack, 
Delabole, and other parts of the County to careful microscopic 
examination and chemical analysis ;* a course of enquiry invol- - 
ving enormous toil, but which must some—lI fear at a distant—day 
ensure practical results of enduring value. 
Mr. Hunt’s periodical accountst of the produce of our quar- 
ries and mines, are so generally known and so justly appreciated 
that they call for no remark from me. 
As my labours amongst our metalliferous deposits have re- 
commended me to your notice, I feel it a duty to offer some 
account of our acquaintance with them. 
The metalliferous series of Cornwall comprehends—granite,— 
slate, possibly of more than one period, associated, in some places, 
with hornblendic rocks,—and elvan which occasionally appears in 
seemingly isolated{ masses, but usually forms broad (courses) dykes 
intersecting both granite and slate. 
The granite occurs in four principal—beside in several 
smaller—bodies ;§ slight differences of composition are not un- 
common ; but—excepting in particular districts—felspar, quartz, 
and mica are the principal ingredients; everywhere, however, 
schorl is more or less abundant. In some localities, at least, the 
felspar and the mica are of two kinds;]|| and in certain parts of 
the County the mica is replaced by talc. An ordinary granitic 
basis often includes large, coincidently-placed crystals of felspar ;** 
and these contain, not uncommonly, both mica and schorl.tt+ 
Microscopic cavities,—sometimes empty, but more frequently 
containing either liquid or gaseous matter,—have been detected 
* Lond: Edin: and Dublin Phil: Mag: xli., pp. 87-107. 
+ Memoirs of the Geological Survey of Great Britain (Mineral Statistics), 
1870. 
+ Thomas, (R.) Survey of the Mining District from Chasewater to Cam- 
borne, pp. 17, 49. Webb and Geach, History and Progress of Mining in 
the Caradon and Liskeard District, pp. 33, 36. 
§ Boase, Cornwall Geol: Tran: iv., p. 362. Henwood, Ibid, v., p. 148. 
|| Haughton, Proceedings of the Royal Society, xvii., pp. 209-211. 
q Fitton, Thomson’s Annals of Philosophy, iii., pp. 189-104. Boase, 
Cornwall Geol: Trans: iv., p. 236. Henwood, Ibid, v., pp. 17, 44, 115-119. 
‘Tt is reported that [Mr. Cookworthy] ... not far from 1755, .. . first 
discovered [China-stone] in Saint Columb Church, or rather in the Tower, 
which is built of stone from Saint Stephens.” PripEAvx, Relics of William 
Cookworthy,.p. 4.. 
** Henwood, Cornwall Geol: Trans: v., pp. 17, 145; viil., p. 682. 
++ De la Beche, Report, p. 190. Henwood, Cornwall Geol: Trans: v. 
_p. 145. Sorby, Quarterly Journal of the Geological Society, xiv., p. 475. 
