ON THE DETRITAL TIN-ORE OF CORNWALL. 205 
Some forty-five years ago* the surface of Perran-Well (Smelt- 
ing-house) vale, at its confluence with the principal valley, was 
from four to six feet below the level of the highest tides ;+ from 
these, however,—as at the upper part of Carnon in earlier years— 
it was protected by an embankment, and wrought as an open-work. 
The ingredients with which it was then filled, to a depth of sixteen 
or eighteen feet, consisted of— 
(as Angular gravel, sand, and silt, the débris of various 
rocks and vein-stones stamped in upper parts of the 
principal valley. mixed with rounded masses of granite 
and slate from the neighbourhood ; in numberless 
beds of unequal—but never of very great—thickness.. 12 to 15 feet; 
At a considerable depth in this deposit the remains of 
deer occurred; and still deeper Oyster-shells were 
numerous. 
(2). Fine silt, mingled with Oyster-shells, leaves, nuts, and 
branches of trees, amongst which the wing-cases of 
beetles might sometimes though very rarely be 
Ghigeenmes! oooodyoooudododoboodbGsouueobOHOu DOOD 6 to 18 inches; 
(3). Zin-ground ; consisting of small—more orless rounded 
—bodies of tin-ore; interspersed with angular and 
subangular plocks of schorl-rock, schorlaceous- 
granite, quartz, quartzose-slate, and other vein-stones 
of both the granite and the slate series of the district 
in much greater abundance .............. o000000C 2 to 3 feet; 
The Shelf ; of homogeneous, thick-lamellar, clay-slate, of silky lustre ; 
traversed, almost meridianally, by a quartzose cross-vein, which was wrought 
throughout the entire width of the vale; and—some twelve or fifteen fathoms 
below the tin-ground—yielded consider, able, though not quite remunerative, 
quantities of argentiferous lead-ore. 
Granules and thin flakes of goldt were now and then—though very 
uncommonly—found in the tin-ground. 
* Pryce, Mineralogia Cornubiensis, p. 136. Thomas, History of Fal- 
mouth, pp. 48, 51. Barham, (C.), Reports of the Royal Institution of Cornwall, 
xlii, (1860), p. 16. Francis, (W.), Gwennap ; a Descriptive Poem, p. 7. 
Henwood, Journal of the Royal Institution of Cornwall, iii, (1870), p. xvii. 
+ At Falmouth ‘average spring-tides may be considered as having a 
“rise and fall of 16 to 17 feet; and these rise to about 18 feet, and fall of 
‘Cabout 13 feet, above the lowest veers. The neap-tides average a rise and 
‘fall of about 7 feet, being at high-water, about 14 feet, and at low-water 
‘about 7 feet, above the lowest veers.” Tuomas, (R.), History of Falmouth, 
66 p. 43. . 
¢ “A piece of gold, in a matrix of quartz, from Carnon Vale, in the Royal 
“ Institution of Cornwall, weighs 11 dwts. 6 grs.” MicHELL, ae ), Manual of 
“ Mineralogy, p. 2. 
“Gold was found in the bed of the brook from Tarnon-dean upwards as 
far as Trewedna-water.” Francis, (W.), Gwennap ; a Descriptive Poem, p. 94. 
My home was less than half a mile from this rivulet; but that any Bert 
of its course had been found auriferous, I never heard until now. 
Cc 2 
