Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/162

I give the provincial names of the rocks as they are in general use among the Cornish miners.

A		—		311	fathoms		Killas
B		—		11	—		Elvane		Chlorite and Quartz
C		—		23	—		Killas
D		—		6	—		Grouan		Clay Porphyry
E		—		12	—		Killas
F		—		26	—		Grouan		Clay Porphyry
G		—	$\left.{\begin{matrix}\ \\\ \end{matrix}}\right\}$				Killas
H	$\left.{\begin{matrix}\ \ \end{matrix}}\right\}$	—		436	—	$\left\{{\begin{matrix}\ \ \end{matrix}}\right.$	Ditto
I		—					Ditto,		with veins of Quartz
K		—		15	—		Elvane
L		—		3	—		Killas
M		—		7	—		Grouan		Porphyry
N		—		12	—		Elvane		Quartz, granular and crystalline
O		—		408	—		Killas
				———
				1270	Whole length of the tunnel.
				———

The direction of all these beds seems to be parallel, and to range nearly east and west.

All the veins that at present are known in the part of the hill which the tunnel will intersect are shewn in the drawing, by lines, which describe their dip as nearly as is ascertained from the little that has as yet been seen of most of them.

Some of these lodes have been discovered by the tunnel, and some are known by old works upon them near the surface.

It was not to be expected that any great proportion of the number would turn out productive of ore, or at least that they should be so at the exact point where the tunnel cut them. One or two, if rich in ore, might render the speculation a profitable one, and it is rather extraordinary that the first which was discovered, at the