Xxi 
also abundant,* and in the slate it predominates.t Between the 
lodes and the rocks they traverse, however, a transition, or—so 
to speak—an assimilation often takes place so gradually that no ab- 
solute line of demarkation can be drawn. Large portions of the 
_lodes which intersect the fossiliferous slates of East Cornwall, con- . 
sist of very white{ crystalline quartz abounding in drusy cavi- 
ties lined with crystals. The superficial parts of many—perhaps 
of most—lodes abound in earthy iron-ore of pale-yellow, brick- 
red, or dark-brown hue, mixed with quartz of, more or less, 
granular character (gossan).§ And whatever may be the principal 
produce of the Jodes elsewhere tin-ore is not uncommonly sprinkled 
through these ingredients.|| When tin-lodes traverse the granite 
their most productive vein-stones are pale-greenish or brownish- 
red felspar, confusedly crystalline, but rarely in distinct crystals, 
mixed with quartz and schorl; sometimes, however, schorl and 
quartz are abundant ingredients; and now and then quartz 
prevails; the tin-ore generally occurs in crystalline granules, 
which seldom exceed the size of pease and are usually of almost 
microscopic smallness ;1 but, for short distances, minute strings of 
cussiterite and schorl occasionally intersect the other constituents.** 
* Berger, Geol: Trans: i., p- 176. Carne, Cornwall Geol: Trans: ii., 
pp. 87, 95. Boase, Ibid, iv., p. 441. Fox, Reports of the Royal Corn: Pol: 
Society, iv., p. 98. Dela Beche, Report, p. 340, Fig. 62. Henwood, Corn- 
wall Geol: Trans: v., pp. 185, 226, 229; vill., p. 675-680. Von Cotta, Ore- 
Deposits, p. 412. 
+ Carne, Cornwall Geol: Trans: ii., pp. 87, 95. Henwood, Ibid, v., 
pp. 184, 228, 229; vill., pp. 677, 706; Edin: New Phil: Journal, xxii., p. 
156. De la Beche, Report, pp. 340-341, Fig. 63, 64. 
+ Microscopic cavities in the quartz of veins ‘‘are the chief cause of 
the very unusual whiteness of the mineral?” Sorpy, Quarterly Journal of 
the Geological Society, xiv., p. 474... 
§ Pryce, Mineral: Cornub: pp. 88-89. Phillips, (W.), Geol: Trans : ii., 
p. 117. Carne, Cornwall Geol: Trans: ii., pp. 95, 122. Fox, Reports of the 
Royal Corn: Pol: Society, iv., p. 95. De la Beche, Report, p. 326. Hen- 
wood, Cornwall Geol: Trans: v., pp. 204-208, 226-227; viii., p. 676-678, 707. 
Thomas, (C.), Geology of Cornwall and Devon, pp. 5, 19. 
|| Phillips, (W.), Geol: Trans: ii., p. 117. Thomas, (B.), Report p. 20. 
Carne, Cornwall! Geol: Trans: ii., p. 102, Fox, Reports of the Royal Corn: 
Pol: Society, iv., p. 85. Dela Beche, Report, p. 326. Henwood, Cornwall 
Geol: Trans: V., pp. 205, 226; vili., p. 677. Von Cotta, Ore- Deposits, p. 413. 
q Henwood, Cornwall Geol: Trans: v., p. 226. 
** Jars, Voyages Métallurgiques, iii., p. 190. Sedgwick, Trans: Cam- 
bridge Phil: Society, i., p. 108; Geol: Trans: iii., p. 483; Phil: Mag: and 
Annals, ix., p. 284. Carne, Cornwall Geol: Trans: ii., pp. 84, 92. Von 
Oeynhausen and Von Dechen, Phil: Mag: and Annals, v., p. 241. De la 
Beche, Report, p. 346, Fig. 67. Boase, Cornwall Geol: Trans: iv., p. 288. 
_ Hawkins, Ibid, iv., p. 476. Henwood, Ibid, v., pp. 15, 119, 226. 
B 3 
