C31 



MINING. 



MINING. 



68J 



The operations which have now been described are applicable to all 

 large and regular metalliferous veins situated in countries where no 

 distinct stratification exists, and where, therefore, from the homo- 

 geneous nature of the rock, the metallic produce may extend to very 

 considerable depths without any great fluctuation. The mining dis- 

 tricts of Cornwall, and those of Germany and Mexico, are chiefly of 

 this class. 



Mining in Stra/tjieil Districts. In working mineral veins in dis- 

 tinctly stratified countries, this geological feature has a great influence 

 on the arrangement of the subterranean works, as it impresses a 

 peculiar character upon the contents of the veins, the metalliferous 

 portions of which are in great measure confined to certain strata, while 

 the intervening parts are poor and unproductive. Thus, instead of 

 exploring the whole mass of the vein, as in the former case, it is only 

 necessary to lay open those limited zones which are embosomed in the 

 strata most favourable to enrichment, and to which therefore the 

 workings are chiefly confined. The lead-mines of North Wales, of 

 Derbyshire, and of the North of England, are worked in the car- 

 boniferous limestone, and the grits and shales resting upon it, the two 

 former being the productive rocks. In these mines therefore the 

 mode of working above noticed is adopted, and, from the abrupt and 

 mountainous nature of the country, great facility is afforded in carrying 

 on the subterranean works, which are generally executed in the 

 following manner. A point is selected in some valley or ravine where 

 the edges of the strata are exposed to view, and from thence a level is 

 commenced, if practicable, upon the vein itself, and in one of the beds 

 known to be favourable to its enrichment, the progress of which 

 effectually explores its produce, and admits of a convenient extraction 

 of the ore. Should the vein itself not appear in any spot from which 

 it can be directly driven upon, the level is driven as a cross-cut till it 

 is reached, being either carried on one of the productive strata, or in 

 some other bed adjoining them which may afford greater facilities for 

 driving. Whenever bunches of ore are found in the progress of this 

 level upon the vein, excavations are carried upwards and downwards 

 into them, as far as the ore extends, thus laying it open in a convenient 

 manner for extraction. Should the ore extend far enough towards the 

 surface to render it necessary, levels may be driven from the " rises " 

 to render it more accessible, and should another productive stratum be 

 situated at no great height above the first, similar operations will be 

 extended into that also. The vein having thus been laid open, the 

 masses of ore are placed in a proper state for working ; they are 

 broken from the vein either by the pick or by blasting, and the works 

 BO arranged that the stuff falls at once into the level below, whence it 

 is transported in tram-waggons to the entrance, near which the dress- 

 ing-floors are usually placed. P'uj. 4 represents the section of a mine 

 worked in the above manner. 



HI.-, i 



As the principal level of a mine worked in this manner is always, 

 when possible, carried at or near the bottom of the lowest productive 

 stratum, the whole process of working may often be carried on by 

 rises, and no necessity will exist for sinking below the main level, 

 which answers the purposes both of drainage and extraction. When, 

 however, other productive strata exist below this, which from the 

 nature of the country are inaccessible by day levels, recourse must be 

 had to sinking winzes below it to explore them. 



When a level has been driven a considerable distance from its mouth 

 or entrance, a shaft will be required, which is usually sunk from the 

 surface so as to come down upon it near the end. The deeper work- 

 ings are then carried on by means of this shaft, which is either con- 

 tinued perpendicularly or upon the vein, till it reaches the next 

 productive stratum, upon which a level will be driven. By extending 

 the day level or adit upon the course of the principal vein, and such 

 others an may be found in its vicinity, and by sinking shafts occasionally 

 where they may be found necessary ; a mine worked in this manner 

 may be indefinitely extended, and its workings arranged so as to be 

 accommodated to the nature of the metalliferous deposits which may 

 be discovered in their progress. 



Although the general principles which regulate the direction of 

 mining operations will best be understood from thus tracing their 

 most important modification from the beginning to a mature and 

 systematic development, it must not be supposed that all mines are 

 invariably worked upon the same plan, or even that the first opening 

 of mines is a thing of very frequent occurrence. The local circum- 

 stances of mines are so exceedingly various, and the irregularity and 

 complexity of mineral deposits so great, that a corresponding diversity 

 must exist in the means adapted for exploring them, and hence, 



although the general principles and features are the same in all, no two 

 mines will be exactly alike, nor would the same unvarying processes 

 be suitable for them. 



Mining Tools and Processes. The tools and processes employed by 

 the miner in the excavation of the rock or the vein are simple, and 

 will require only a brief notice. As his work is chiefly of two kinds, 

 simply excavating the ground when soft, and blasting it when hard, 

 his tools are suited to each process, the "pick" and "gad" being used 

 for the former ; the "borer" or "jumper," and the " hammer " used 

 to propel it, for the latter, with several minor accessories for firing the 

 shots, when the hole has been completed to its proper depth. The pick 

 ia a very useful tool and much employed by the miner both in working 

 in the rock and in breaking down ore where the ground is not so hard 

 as to require blasting. It resembles a common pickaxe, but is smaller 

 and more convenient, the iron head being sharp and pointed at one 

 end, and very short and hammer-shaped at the other, a form which 

 peculiarly adapts it to underground uses. The wedge or " gad " is 

 sometimes used in conjunction with the pick ; it is made of wrought- 

 iron, and often with curved sides. The borer or "juniper " is an iron 

 rod or circular bar usually about two feet in length, steeled and formed 

 into a flat sharp edge at the end ; it is driven into the rock by one 

 man with a heavy hammer, while the other continually turns it round 

 so as to expose the cutting edge to fresh surfaces of rock. The 

 pulverised matter is drawn out from time to time by a tool called a 

 " scraper," and when the hole has proceeded to a sufficient depth, and 

 been charged with powder, an iron wire with a copper point, or, what 

 is still better, a piece of copper wire, with a loop at the end, is intro- 

 duced, when the charge having been firmly rammed down with clay or 

 other soft mineral substance, the wire or " needle " is withdrawn, and 

 a train of gunpowder inserted in its place. The train is then fired by 

 a slow match (often a piece of brown paper smeared with grease), aud 

 the miners retire till the explosion has taken place. A very ingenious 

 contrivance for firing the charge was invented some years ago iu Corn- 

 wall, by Messrs. Bickford, called the " safety fuse," which is now getting 

 into very general use in our mining districts. The safety fuse consists 

 of a small train of powder inserted in a water-proof cord, and being 

 cut to the required length, regulates the time of the explosion by its 

 known and steady rate of ignition. The use of this contrivance and 

 the substitution of copper for iron in the " needle," have contri- 

 buted of late years to prevent the accidents arising from premature 

 explosion, which were formerly of very common occurrence in mines. 



Auxiliary operations. Having now considered mining in the most 

 simple point of view which the subject admits as the arrangement of 

 a system of subterranean works adapted to effect the great objects of 

 discovery, extraction, ventilation, aud drainage, it remains to notice 

 the various auxiliary operations which the progress of these works 

 will have required, 'and the complicated machinery which will thus 

 have been called into action, both on the surface and underground. 

 The auxiliary works in question will have been directed towards two 

 distinct objects, one portion of them being subsidiary to the actual 

 working of the mine itself, and the other directed to the mechanical 

 preparation of the ores extracted, so as to render them fit for the 

 smelting works, to which they are finally consigned for reduction, this 

 last process being sometimes carried on upon the spot and by the same 

 parties, and in other cases being performed at a distance by a distinct 

 agency. We now proceed to cousider the former of these two 

 classes. 



The underground works of a mine will not have proceeded far before 

 it becomes necessary to provide for several very important contingencies ; 

 water filters rapidly in, and, excepting where mines are worked by 

 day levels or adits (or even then on sinking below them), requires some 

 power to be provided for drawing it out; excavations are formed 

 which require support ; ventilation in places requires to be aided by 

 mechanical means ; and lastly, the continually increasing extraction of 

 ore and rubbish renders powerful and efficient means indispensable for 

 its discharge. 



liminaije; Horse-Whim. The drainage of a mine is one of the 

 earliest things which it becomes necessary to provide for, as mineral 

 veins are generally more open and porous than the surrounding rock, 

 and thus form natural reservoirs into which the surface water collects. 

 When penetrated by the workings of a mine, this natural drainage i.-i 

 rendered still more complete, and water pours abundantly into the 

 excavations. The most obvious mode of relief, where local circum- 

 stances are favourable, is of course the formation of an adit, but ex- 

 cepting in very abrupt and mountainous countries, where this work 

 can be readily executed, mechanical power soon becomes necessary. 

 This may be in the first place afforded merely by a " horse-whim," 

 which will serve to raise both the water and the stuff broken in sinking; 

 and in Mexico, before English skill and capital were applied to the 

 working of the mines, this simple apparatus was the only power used 

 in their drainage and extraction. Its application on the large scale is 

 however so enormously expensive, so complicated, and so inconvenient, 

 that in the mines of Europe it is only used upon a limited plan, and 

 mechanical power is substituted as soon as possible for animal labour. 

 The machiue alluded to consists of an upright shaft carrying a large 

 cylindrical cage or drum, and turned round by a long lever, to which 

 the horses are attached. A rope is coiled round the cage of the whim, 

 with both ends at liberty, so that while one end is winding up, the 



