LODE. 



vfry profitable to work, and is called a fjood emrfe of ore. 

 Tlic variations of width take place not only in dillinft veins, 

 but in one and the fame ; wliich, together with the fluctua- 

 tions in the nat\ire of their contents, render their produce fo 

 uncertain. A large and produclive lode often dwindles to 

 a mere branch, requiring an experienced eye to dillinguifh it 

 from the rock tiirough which it pafies ; and this again ex- 

 pands to a confiderable ii/.e, filled with depofits of various 

 kinds. The width of lodes fecms often to have a relation 

 to the nature of the rock in which they are found ; and 

 changes in the latter appear generally to produce changes in 

 the former. Thus, a vein that is large and produftive in 

 foft blue kiihis, will, by pafling into harder, become lefs in 

 fize, and barren as to metallic contents. Aiiothcr lode may 

 be rich in hard ground, but poor and unprodudlive in that 

 which is of a fofter kind : but this is not fo frequent as the 

 ibrmer cafe. The depofits of metal are as iiregular in the 

 lodes as tlie widths of them ; and fo much fo, as to render 

 the proilts of mining proverbially uncertain. Ore is gene- 

 rally found to occupy certain parts of the veins only, dif- 

 fering conftantly in extent, whether the length or depth on 

 the cocrfe of the vein be coi^fidered, or the portion of its 

 width which is filled up by it. No lode has been found re- 

 gularly impregnated with metal to any great extent ; and 

 therefore, when ore is found, it is in what the miners aptly 

 call bunches or Jhoots. The uiiproduillive parts of veins, 

 €ven in the mull profitable mines, generally far exceed in 

 extent the produdive parts ; but that mine is confidered to 

 he rich, which has either frequent or extenfive Ihonts of ore : 

 the great art of the miner, therefore, confills in tracing 

 and working the valuable accumulations of the metals with 

 as little wafle of labour and expence on the poorer ground 

 as pcflible. 



Although the bunches of ore have no regular form in their 

 vertical or horizontal extent, yet the tendency to a certain 

 direction or dip in the lode may be obferved in each bunch 

 or flioot of ore. Thefe llioots are frequently parallel in the 

 fame vein ; and where the dip or underlay of the lode is to 

 the north, the fhoots of ore may frequently be obferved to 

 dip well in the lode. In veins underlaying fouth, the 

 bunches of ore frequently have their dip to the eaft : but 

 this is not to be taken as a general rule, as many mines af- 

 ford exceptions to it ; tlie underlay of the lode and the dip 

 .of the bunches of ore being reverftd. 



Tliefe tendencies or inclinations of the depofits of metal 

 in the veins, connected with the fitnations, dips, and bearings 

 .of the veins theinfelves, feein to offer grounds for argument 

 en the difputed quellion of the mode it) which the metals 

 were dcpohtcd ; but they have not much, we believe, at- 

 tracted the notice ot niineraiogifts. 



Lodes continue to indefinite lengths, and to unknown 

 depths. It is very difficult to determine whether the end of 

 any regular vein has been found or not ; as there are many 

 inllances of their having become fo fmall as to be fcarcely 

 vifible, and yet afterwards, on purfuir.g them, to have rc- 

 funied their ufual fize. When a lode has continued fmall, 

 . either in length or .dtplh, to any confiderable extent, it is 

 moreover ufually abandoned as unpromifing ; and thus com- 

 ,plete evidence as to this queltion is net obtained. 



Lodes are perfect in the f'.irface of the mountains, as well 

 as in tlieir greater depths ; and may be traced uniformly by 

 removing the foil v.ith wliich the rock is covered. This is 

 done conllantly bv the miner when he is about to undertake 

 operations upon a newly difcovered vein. Th.s procefs is 

 called cojlemin^, or Jhod.T,g. The width of a lode at the 

 furface is noceitain indication of its fize in depth: as, when 

 large at the .furfacc, they are fomelimes ftiuad to become 



fmall ae they arc purfued downwards ; and, on the other 

 hand, veins of moderate width a! graft have been found, at 

 40 or 50 fathoms deep, of gr*at fize. 



The dip or inchnation of lodes is feldom uniform. The 

 common underlay is from one to four feet in a fatliom of 

 depth ; but inllances occur of a much greater inclination. 

 The lodes that incline much from the perpendicular are not 

 elleemed fo promifing as tiiofe which have a direction more 

 downright ; and it is a favourable fymptom wlicn a lode, 

 from an oblique direction, is found to turn downwards. On 

 the contrary, where bunches of ore fall, or become poor, in 

 finking on them, it may often be obferved that the vein goes 

 away flat, as miners exprefs it. Thus it will be underllood, 

 that not only are the dips different in. feparate lodes, but 

 that the fame vein frequently varies in this refpc£t. Lodes 

 have been obferved to change their underlay, tliat is, from 

 dipping to the north, to become perpendicular, and even 

 turn to the fouth. This is not, however, a matter of fre- 

 quent occurrence. 



The underlay of lodes muft be afccitaincd, when it is in- 

 tended to fink perpendicular fliafts to meet them at certain 

 required depths ; and from this is determined the diltance to 

 be fet out north or fouth from the back of the vein, for com- 

 mencing fuch fliafts. 



Shafts are of/^n funk upon the lodes, and of courfe thefe 

 are not perpendicular, but have ,the fame inclination as the 

 veins. 



Levels driven from the fliafts, are carried on in the fub- 

 ftance of the lode, follow its dircflion, and are the prin- 

 cipal means by which difcoveries of ore are made and pur- 

 fued. 



The principal methods by which lodes are difcovered are 

 the two following: i. By removing the foil covering the 

 furface of die rock, by which the back of the vein is laid 

 bare, and expofcd to view. This may happen accidentally, 

 in the formation of roads, ditches, and fo on ; or, as is more 

 ufual, it may be done for the exprefs purpofe of difcovery, 

 in confequcnce of indications of veins being near at hand, 

 fuch as detached fragments being found, or fprings of water 

 impregnated with metal being obferved. This procefs is 

 condudted by finking trenches, or pits, deep enough to 

 reach the furface of the rock, called by miners the fhelf; 

 which trenches are CdiWeA Jhodlng pits, or cnjieening pits. I'lie 

 detached fragments, warned from the backs of lodes, are 

 ufually c-sWtA Jhcdes, or fhodeflcnts. 



The fecond mode 01 difcoverirg veins is by levels, or 

 horizontal cuts, driven under ground, which in their pro- 

 grefs through the rock, or, as the miners fay, acrofs the 

 country, interfeft and expofe lodes before unknown. Such 

 levels muft have a direction acrofs the ufual courfe of tlte 

 lodes, and are either condufted for the exprefs purpofe of 

 finding new vcini, or for fome other ubjedt ; and then may 

 occafionally be the means of valuable refults of this fort. 



Many rich mines have been opened, in confequence of a 

 difcovery made by carryir.g on an adit, or by driving a crofs 

 level from a fliaft, or from one lode to another known to be 

 parallel to it. The practice of driving adits for the pur- 

 pofe of difcovery is more frequent than it ufed to be. The 

 Tavillock canal has a long tunnel driving through a hill, 

 deftined principally for this purpofe, and which has already 

 been attended with very great fucccfs. 



Lodes feldom contain ore near tlie furface of the ground : 

 it is, therefore, an effential quality in a miner's judgment 

 to decide on the indications prefenled by them, and to de- 

 termine the amount of rifk which their appearances will war- 

 rant on a further trial. 



There arc niceties in this bufinefs which cannot be dc- 



IcrJbed, 



