MINKfiAL VKIXS 
80 
oi'cs of silver, or ti uo silver rninoj als, are almost sure to be accojnpanied 
by some, though perhaps not a woi-kable rjuautity, of the ores of lead or 
zinc, to say nothing of that ubiquitous, cornrnon-]dace, yet often beautiful 
associate of tlie otlier ores, li-on I^yj-ites. Certain disti'icts are notable 
foi' the tejuJeney of the veins to be small ami comparatively l ich, as foi- 
instance some of oui- Cornish granite regions with theii- ‘'strings” and 
“ branches” of tin-stone ; but wlien the lodes attain greater power, or 
occupy a wide]- space between thei)* walls, the filling will almost in¬ 
variably be found to be of a mixed chai-actej-, and to offer in different 
portions of their extension extj-ernely varial^le appearances. Hardness 
and softness, povej-ty and riches, may suddenly succeed each other, or 
may, either of them, continue for long distances, with ever-changing 
phases of size, mineral, and colour, amid the complexity of which the 
adventurous miner must 0{)en the rocky gj-ound ijjch by inch and fathom 
by fathom, basing his opinion, as long tin the result remains uncertain, 
on the analogy of the phenomena undei- his eye with those which have 
been encountm-ed elsewho-e. it is thus that the structure of the matrix 
or body of the lode rnatei-ial, the particular association of minerals in it, 
an<l an infinite numlicr of slight shades of physical variation, hardly 
ca]»able of being expi-essed in woi-ds, interest alike the explorer rnatuiing 
Jiis judgment on the probal^iJities of success, and the philosopher 
studying the workings of Nature in these her remote and teeming 
laboratories. 
Kegulai-, well formed lodes may often be t)-aced for a mile or two in 
length, some few, as in the Jfai'tz, Hungary, and in Wales, as much as 
four 01 ' even eifrht or nine miles. Descending v/ith an inclination rnoi-o 
or less vai-iable, they continue to the greatest depths to which man has 
attained, and are nov/ Avorking in the FoAvey Consols Mines, CornAvall, 
at a depth of 340 fathoms from the surface, at i'^rzibram in llohemia at 
370, and at Andreasberg in the Hai-tz at 42(? fathoms, dejdhs of Avhich 
the clearest idea may be obiained Avhen Ave remember that they represent 
the height respectively of ten and of tAvelve Monuments of London piled 
one on the top of the other. 
4'he general traits ef the simpler veins are well illustrated by the 
fissures of contraction Avhich have taken place in the nodules of ironstone 
occurring so largely in the coal measui-es. Some of these, and particularly 
certain bands found in South Wales and in Derbyshire, exhibit the cracks 
sometimes partly open, and at others filled with minerals of subsequent 
introduction, among Avhich are the carbonates of iron and lime, quartz, 
millerite, zinc-blende, galena, copper and iron pyrites. Crystals of the 
latter four sulphides, iii the midst of what Avas once a sea sediment, and 
sometimes CAuni attached to fossil remains, prove the for-mation of such 
compounds from AA'ateiw solution. The ser ies commences Avith a number- 
of examples of this kind on a mirjiature scale, in Wall-case 24 ; andAve 
pass thence to the sti-ings or small veins Avhich are formed for the most 
part of one simple mineral. Veins of this kind are seldom traceable for 
any consider-able distance, arjd ar-e commonly only subsidiai-y to, or 
connected in some AAuy with, the sti-onger lodes of a district. 
With the increased bulk of the regular lodes becomes also noticeable 
the prevalence of certain directions for those which contain the ores of 
particular metals ;—thus E. and W., or E.N.E. and WbS.W. are the 
prevailing directions of the tin and copper lodes of Devon and Cornwall, 
