

MI> 



MINING. 



i , | 

 liferous deposit* U aflbrded 



eeise indication of the existence o( metal- 

 by finding pebble* or fragment* of ore on 



or near the surface, generally either in the bed* of streams or mixed 

 up with superficial detritus. Theee scattered fragment*, the remit of 

 diluvUl action upon the outcrop of mineral rein* or other deposits, 

 may often be traced to particular ipot*, and thiu the position of the 

 deposit* from which they originated may be established. In the north 

 of England they ore termed " aboad atones," and this mode of di 

 covering veims i* called " sheading." Should the exact situation of the 

 vein whose nrlfrtitni-n has been ascertained in this or any other manner 

 not be observable, it may be aroartained by opening trenches in the 

 alluvial aoil deep enough to expose the solid rock, their direction K-ing 

 at right angles to that in which analogy or the position of oth< . 

 in the neighbourhood would render it probable that the vein or vein* 

 in question might lie. This mode of finding vein* is prorincially ter- 

 med in Cornwall " costeening." The object of discovery may be still 

 more effectually attained, but at a greater expense, by excavating a 

 nearly horizontal passage termed a " level," " drift," or " adit," front 

 the bottom of the nearest valley, carrying it through the solid rock in 

 the direction before mentioned, so as to intersect or " cut " any mineral 

 deposit which may exist in the ground through which it passes. This 

 last plan is however seldom adopted, unless it is previously well ascer- 

 tained that mineral veins do actually exist there, as it is too slow and 

 too expensive to be undertaken upon uncertain grounds. Discoveries 

 are sometimes made also by driving on the course of veins which occur 

 in cliff* or are exposed in the sides of brooks ; trials of this kind fall 

 within the compass of working miners or persons of very small capital, 

 and in some instances form the first step in opening mines which ulti- 

 mately become of great importance. 



Although the manner in which mineral deposits may be and some- 

 times are originally discovered has been thus detailed, it must not be 

 supposed that the process is one of very frequent occurrence. Tlu> 

 principal mineral districts in this and most other countries have been 

 known and explored for ages, and by far the greater part of our 

 mineral produce is extracted from deposits which have long been 

 worked, the principal new discoveries being either made upon untried 

 portions of known veins, or simply by excavating passages or " cross- 

 cuts " from mines now working, in a direction transverse to that of 

 the vein upon which they are wrought, so as to prove the adjoining 

 ground. 



Financial arrangement*, A-c. When however a new vein or mineral 

 deposit has been by any process discovered, if the indications of metallic 

 produce are such as to render it desirable to work it, the moat usual 

 step, after obtaining the consent of the proprietor, is the formation of 

 a company for this purpose. For although mines are sometimes worked 

 by individuals, experience has shown that a company is best adapted 

 for carrying on mining operations, the amount of capital required being 

 large and uncertain, and the risk great, while a long period may elapse 

 before adequate returns are made. Hence, not only in Kngland, I nit 

 in most other countries, the system of working mines by companies 

 has been adopted, being found decidedly advantageous. Certain stipu- 

 lations are then entered into between the company and the proprietor 

 of the land in which the vein or deposit is situated, or, should tlio 

 mineral ripht not belong to him, with the person who does possess it 

 The principal terms of this agreement are to determine the extent of 

 ground within which operations may be carried on, and to stipulate 

 the proportion of the groat mineral produce or it* equivalent in money 

 which the owner is to receive free of all expense in raising and making 

 it marketable. It often includes also compensation for damage done 

 to the surface, and other considerations of less importance which are 

 determined by the custom of the neighbourhood and other circum- 



Before commencing operations, it is necessary to ascertain with some 

 correctuess (if it should not bo previously known) the bearing or 

 direction of the vein, and also its dip or " underlie," which may be 

 done by sinking a few shallow pits upon it. These circumstances being 

 known, there are two methods by which the vein may be explored, 

 either by sinking upon it* course from the surface, or by forming a 

 horizontal passage to intersect it, commenced from some neigli! 

 valley or the lowest point on the surface which may be conveniently 

 Moated for the purpose; or both these modes may be carried on 

 together if desirable. As, however, the practicability of forming a 



level or adit to prove the vein at a sufficient dq>th and within 

 rate limit* as to time and expense must entirely depend on local 

 circumstances, the former method, as being most expeditious, is 

 generally resorted to, and is effected in the following manner. 



Early Pragrea of Ike Work*. A spot determined either by conve- 

 nience or by some promising indication is selected as the site of a shaft, 

 which is frequently stink in an inclined direction upon the course of 

 to* vein, or if intended to be perpendicular it is commenced upon that 

 joe towards which the vein inclines or underlies, and at such a distance 

 from it* " back" or outcrop as to come down upon it nt a given depth, 

 soy 10, 20, or So fathoms. This depth is regulated by the means of 

 the parties to prosecute the trial, and the depth at which analogy mar 

 lead them to suppose that ore in any quantity may I 

 superficial part* of veins being usually quite unproductive. 



On cutting the vein the abaft is for a time suspended, and two hori- 

 zontal passages, often termed "(Deries," but by the miner " levels," 



are excavated or " driven " upon the vein in both directions. These 

 passajins are usually about six feet in height and three or four in 

 breadth, and rather smaller above than below. They are the principal 

 means of exploring the content* of veins, and are made larger or 

 smaller according to their richness or poverty, their width, and the 

 nature of the inclosing rock. Should the shaft be intended to cut the 

 vein at any considerable depth, it may be desirable to explore it above 

 the mint of intersection, and this is done by driving a short transverse 

 level or " cross-cut " to it, and driving two levels from the place where 

 the "cross-out "meets it, as before described, sh.ml.l t 

 the shaft before reaching the vein be very considerable, two or 

 of these cross-cut* will lie driven first, and levels ext !:,! 



The perpendicular distance of the levels from each other is nv 

 both by custom and local circumstances, but is usually about in 

 fathoms, that interval having been found most convenient for the 

 objects of the miner. 



After cutting the vein there are two modes of procec nniin; 



the shaft perpendicularly through the vein, or obliquely upon the vein. 

 Which of these two plans is followed will depend in great measure 

 upon it* produce and promise, as already ascertained by the 

 levels, and partly also on the means of the miner, the former pi, 

 being most expensive and requiring the longest time, although ulti- 

 mately most advantageous, while the latter, though a cheaper and 

 quicker mode of exploring the vein, since it renders cross-cuts unneces- 

 sary, and is itself continually proving one portion of it, is not well 

 adapted for the application of pumps and machinery, an evil which 

 may not at first be very sensibly felt, but which increases proportionally 

 with the depth of the mine and the quantity of water and stuff which 

 require to be drawn from it. 



Supposing the shaft to proceed perpendicularly after cutting the 

 vein, on reaching the depth of 10 fathoms or thereabouts below the 

 point of intersection another cross-cut will be driven to it ; but as the 

 shaft is now on the opposite side of the vein, this cross-cut will have an 

 opposite direction to the former ones ; and as they had successively 

 become shorter as the shaft approached the vein, they will now succes- 

 sively become longer as the shaft, proceeding perpendicularly down- 

 wards, recedes further and further from the vein. In this manner the 

 shaft proceeds indefinitely, cross-cuts being driven at every 10 fathoms 

 or whatever distance is moat convenient, and levels extended from each 

 upon the course of the vein, the nature and value of which are thus 

 thoroughly explored. The continuance of these and other opei 

 necessarily supposes that ore in some quantity has been found in the 

 upper levels, which will have been all this time in progress, or at any 

 rate that the indications of future produce are sufficiently strong to 

 encourage the miner to proceed with his undertaking, the magnitude 

 and expense of which will now be daily increasing, while various diffi- 

 culties will be encountered in the progress of his works, more 

 especially the want of ventilation in those parts which are most distant 

 from the shaft, by which alone they can be supplied with air. 

 chiefly in the ends of the levels that the evil of imperfect ventilation 

 begins to be felt, the air here gradually becoming close and unlit for 

 respiration as they advance further from the shaft, especially when, 

 from the hardness of the ground, frequent blasting is necessary. As 

 soon as this is found to be the case a remedy of.a very simple, nature 

 i- applied, which consists in sinking a small pit, termed a " 

 upon the vein, of course, from the upper level to the extremity of the 



o:ie below it. This COmmunic<lti"M liaun,' been effected, ll. 



become perfectly ventilated, each In !e communication with 



the atmosphere, by which both an ascending a- :>^ current is 



produced. By this plan it is evident that the 1 



for a considerable distance upon each side of the shaft, winzes being 

 continually formed between them at convenient intervals. Besides the 

 purpose of ventilation, these winzes answer another use, since they 

 make trial of the vein in the intermediate space between two levels, 

 and also divide it into solid rectangular masses, which may be examined 

 .ill round, and thus the miner has the means of judging with tolerable 

 certainty of the nature and value of the ores rout li, and 



can extract the produce in the most expeditions and economical 

 manner. That such is the case will at once be evident when it is con- 

 sidered that these portions of the \cin are perfectly drained ami 

 ventilated, that they may be attacked at once from an many p 

 may be convenient or may contain ore of sufficient value, and from 

 this circumstance no necessity exists for breaking down the nnpro- 

 ductivc masses which are often found to intervene even where tl 

 is richest and the ore most continuous. When the vein has been 

 properly laid open, the ore may be worked away round such > 

 ductive pieces of ground, which" being left standing, will answer the 

 purpose of supports to the rock on each side of the vein. Where the 

 excavations are extensive such support becomes extremely necessary, 

 mid often requires the use of strong 



The utility of winzes for working out the ore is indeed so great, th.it 

 it is only when little or no ore has been found in a level that it will 

 have proceeded far enough for ventilation to become very den 

 before a communi' 'in kind has been made. When, on the 



contrary, the .nnous in driving a level, 



winzes are generally sunk at intervals <>f 2u or .'!n fathoms, their 

 position being so regulated as to prove the richest and most promising 

 parts of the vein, and to avoid hard and unproductive portions which 



