ot ON THE DETRITAL TIN-ORE OF CORNWALL. 
especially,—and to a less extent in several other districts*—it is 
scattered through—and, so to speak, forms an integrant part of— 
the granite ;+ and in the slate series, north of the granite; tin- 
ore is interlaminated with schorl and quartz.| All—save one of 
—these spots have, however, remained unwrought for many years. 
In, and on the confines of, the district iron-ores abound.} 
The detrital deposits of tin-ore on the west and south have 
been often and minutely described,§ but they are now nearly if 
not quite exhausted ; those towards the north and east have how- 
ever, attracted less notice,|| and on some of them operations are 
still carried on. 
A comparatively low ridge of slate stretches—some 30° W. of 
N.—E. of S.—from the granite of Hensbarrow{ to that of 
Belovely Beacon, dividing the upper waters of the Roche (Par) 
“Carclase tends to unfold the origin of the tin-ore scattered in grains 
‘over the bottom of some of the Cornish valleys;...the whole mass of the 
“‘ growan composing the eastern part of the hill, contains these grains....The 
‘strata containing the greatest abundance of tin grains are harder [than the 
“‘ rest] but they are easily decomposed.” Dr Luc, Geological Travels, iii, p. 342. 
““The enormous open-work of Carclase is excavated in a variety of 
“decomposing stanniferous granite or schorl rock.” Sxpewick, Trans: 
Cambridge Phil: Society, i, p. 108. 
Sedgwick, Geol: Trans: iii, (N.S.), p. 483. Henwood, Cornwall Geol: 
Trans: Vv, p. 119. 
* On Dartmoor (Berger, Geol: Trans: i, (0.8.), p. 120) ; at Saint Just 
(Henwood, Cornwall Geol: Trans: v, pp. 15, 235); in Breage (Ibid, p. 53) ; 
and at St. Cleer (Jbid, viii, p. 664.) 
+ Boase, Cornwall Geol: Trans: iv, p. 252. Henwood, Ibid, v, p. 120 
Note*. 
t Dela Beche, Report, pp. 303, 617. Henwood, Cornwall Geol: Trans: 
v, p. 128. 
§ Ante, p. 191. 
|| Henwood, Cornwall Geol: Trans: iv, p. 60. De la Beche, Report, 
p. 405 
q| Hensbarrow ....is 1,034 feet above the sea ;— 
Killivreth Down ,,1,000  ,, a 
Castle an Dinas ,, 729  ,, i 
Belovely Beacon ,, 765  ,, i 
Helmen Tor OS. 6, oA 
De ta Becue (MactaucHian), Report, pp. 14, 16. 
