Xvill 
other parts of their course. Moreover, portions of similar rocks 
occupy different positions on the opposite boundaries of many-lodes ; 
whilst numerous beds and veins, of unlike character, appear in one 
side only but have no existence in the other.* Both in structure and 
composition the lodes are closely related to the rocks immediately 
adjoining them. Their structure, like that of the rocks, seems in 
some measure dependent on their mineral characters. Where their 
composition is most uniform they consist chiefly of quartz; and 
there—as in the homogeneous clay-slates—a jointed structure fre- 
quently prevails ;t but in the more mixed and heterogeneous— 
which also form the largest portions of the /odes—this character is 
less common. The quartzose parts are often traversed by joints 
having the same directions as the Jodes themselves; which are thus 
divided lengthwise into subordinate veins, plates, or combs. 
These joints, however, do not long continue distinct and apart, 
for like joints in the rocks, they curve, unite, separate, and again 
fall together ; thus dividing the substance of the /odes into irre- 
gular plates or slices, which generally thin-off above, below, and 
at the ends, whilst the thicker portions of some adapt themselves 
to the thinner portions of others. When the lodes comcide in 
direction with the joints of the rocks, they appear to be bounded 
by smooth walls ; but when the joints disappear, and—as in many, 
if not in most, cases—there is a gradual transition between the 
vein-stones and the containing (Country) rocks, the walls are said to 
be rough. The lodes not only afford instances of a jointed struc- 
ture parallel to their strike, but they are frequently traversed by 
cross-joints also;§ and examples of thick lamination, or horizontal 
bedding are not uncommon. Near the separation between the 
lodes and the Country the joints are frequently filled with (flucan) 
unctuous clay;|| and this—hke the (Slickensides) glossy surfaces 
of copper-pyrites, iron-pyrites, galena and other ores—is often 
scored with curved, crooked and unconformable striz, which 
—within short distances—not only dip differently—often indeed 
* Boase, Primary Geology, pp. 174-178. Henwood, Cornwall Geol: 
Trans: v., pp. 50, 196, 197; vili., pp. 702-703, Fig. 32. 
+ Pryce, Mineral: Cornub: p. 95. Henwood, Cornwall Geol: Trans: 
Von 19> U7 
t Boase, Ibid, iv., p. 448; Primary Geology, p.179. Fox, Reports of 
the Royal Cornwall Polytechnic Society, iv., p. 90. De la Beche, Report, 
p. 339. Henwood, Cornwall Geol: Trans: v., pp. 179-182; viii., pp. 680-681. 
Von Cotta, Ore-Deposits, p. 416. 
§ Pryce, Mineral: Cornub: p. 95. Carne, Cornwall Geol: Trans: ii., 
pp. 64, 120. Henwood, Ibid, v., p. 181. Fox, Reports of the Royal Corn: 
Pol: Society, iv., p. 93. 
|| Pryce, Mineral: Cornub: p. 93. Fox, Reports of the Royal Corn: Pol: 
Society, iv., p. 90. Henwood, Cornwall Geol: Trans: v., p. 181. 
