XXXV 
sected by them. The cross-veins cut through both ; but whilst— 
in one part or other of their vertical range—they heave hundreds 
of the Jodes, they displace scarcely half a dozen of the scores of 
interlying elvans which they intersect in the selfsame mines.* 
Of vertical intersections we possess only sixteen examples ; a 
number insufficient to afford grounds for safe conclusions. It is, 
however, not unworthy of remark that the (Leaps, Throws) dis- 
placements. of fin-lodes by slides are upward and towards the 
smaller angle; whilst copper-lodes present either simple intersec- 
tions or leaps downward towards the greater angle.t} 
Whether exploratory works are opened in (cross-cuts) drifts 
through the (Country) rocks for recovering lodes which have 
been (heaved) displaced by cross-veins, or on the courses of the 
lodes themselves in search of the ores they contain, they must 
—of necessity—be directed immediately towards, or as imme- 
diately from the object of pursuit. But, although it is im- 
possible to overvalue general rules for the guidance of the miner, 
it must be confessed that neither practice nor theory has yet 
supplied any of general application. A more extended ex- 
perience, and a more careful array of facts seem our only 
resource. But when the vast variety of ever-changing circum- 
stances is considered, we can only hope that our conjectures 
will at length attain greater probability ; and that—if they fail 
of absolute certainty—they will, at least, lead us nearer to the 
truth. 
As no undertaking can be advantageously, or, perhaps even 
safely, carried on without knowledge of its current financial 
operations ; it is important that the speculator should learn the 
general results attending mining proceedings on a large scale. 
* Hawkins, Cornwall Geol: Trans: i., p. 151, Pl. v. Williams, Geol: 
Trans: iv., p. 142, Pl. vii., Fig. 1. Thomas, Mining Review, No. viii., (1836), 
p. 275. Boase, Primary Geology, p. 54. Henwood, Cornwall Geol: Trans: 
v., pp. 67, 90, 91, 104, 127. 
In one well-known case a cross-vein which is heaved by a lode heaves two 
other lodes ; the several portions of one of them being contained in slate on 
one side of the cross-vein but in elvan on the other. The elvan itself is 
simply intersected. Henwood, Reports of the British Association, vi., Part 
ii., p. 74; Cornwall Geol: Trans: v., p. 325. 
The displacement of two lodes by an elvan at Polgooth, described, in 
1791, by Captain Phillips to Mr. Hawkins (Cornwall Geol: Trans: i., pp. 
151-152, Pl. v.), was carefully examined by me in 1831, (Cornwall Geol: 
Trans: v., pp. 128, 327, Pl. ix., Fig. 10). 
+ Henwood, Cornwall Geol: Trans: v., p. 332. 
C 2 
