ON THE DETRITAL TIN-ORE OF CORNWALL. ~ 211 
wards the south-east they assume an arenaceous character, and 
are charged with organic remains.* The elvans which traverse 
the western—but do not reach the easternt—part of this district, 
are well known, and have been frequently described.t The odes 
take a mean direction of about 13° N. of E.—S. of W.,§ but— 
as in other regions—they are not strictly parallel; their diver- 
gences, however, are by no means uncommon. Throughout the 
County their average dip is about 70°, but in this neighbourhood it 
scarcely exceeds 60°.|| In the massive-felspathic, and soft schis- 
tose, rocks on the E. and S.E. they yield copper-ore only ; but 
in the hard, quartzose, thick-lamellar slate, in the schorl-rocks, 
and in the granite towards the N. and W.—though they are 
sometimes sprinkled with the compounds of nickel, of cobalt, of 
uranium,** and of antimony—tin-ore prevails.t+ But Jodes are 
not only the repositories of tin-ore; for in this neighbourhoodtt 
* De la Beche, Report, p. 351. Henwood, Cornwall Geol: Trans: v, 
pp. 125, 158. 
+ Henwood, Cornwall Geol: Trans: v, p. 126. 
+ Bonnard, Journal des Mines, xiv, p. 446. Hawkins, Cornwall Geol: 
Trans: i, p. 150, Pl. 5. Boase, Ibid, iv, pp. 277, 279. Henwood, Ibid, v, 
pp. 126, 160. Dela Beche, Report, pp. 181, 332. 
§ Henwood, Cornwall Geol: Trans: v, p. 250, Table, ciii; Journal of 
the Royal Institution of Cornwall, No. 18, p. xvi. De la Beche, Report, p. 305. 
|| Henwood, Cornwall Geol: Trans: v,p. 247; Annales des Mines, 6me 
Série, ii, p. 172. 
q De la Beche, Report, p. 335. Henwood, Cornwall Geol: Trans: v, 
p. 128. 
** Williams, (R. H.), Reports of the Royal Institution of Cornwall, 
XXxXix, p. 32. 
++ Borlase, Natural History, p. 18. Jars, Voyages Métallurgiques, iii, p. 
108. Bonnard, Jowrnal des Mines, xiv, p. 446. Hawkins, Cornwall Geol: 
Trans: i, p. 146; iv, p. 476. Carne, Jdid, ii, p. 92. Von Oeynhausen and 
Von Dechen, Phil: Mag: and Annals, v, p. 241. Sedgwick, Ibid, ix, p. 284. 
Boase, Cornwall Geol: Trans: iv, p. 276. Henwood, bid, v, p. 120, Tables, 
Ixxxiv, Ixxxv. 
ty ‘‘Il existe pour ainsi dire partout, aux environs de Saint Austell, soit 
“4 la surface, soit 4 quelque profondeur, dans la plus grande partie des 
“ plaines incultes, ot il y a de petits filets d’eau. On peut, en prenant une 
« pelletée de la terre tourbeuse, qui est a la surface, et ’exposant au courant 
“du ruisseau, obtenir par le lavage une quantité sensible de minerai d’étain 
‘cen particules trés-fines, qui se précipitent tout de suite, et que l’on purifie 
‘“‘ par plusieurs lavages successifs. C’est aussi ce que l’on fait dans beaucoup 
“ @endroits avec bénefice.” Bonnarp, Journal des Mines, xiv, p. 450. 
