MIX 



MIX: 



_ of the ground (one fathom per week being a very good 

 average, and sometime, half that progress being scarcely attainable), 

 and** the moot productive working* of a mine may be greatly impeded 

 for want of another outlet to the surface, expedition is often of the 

 utmost importance to remedy this evil, and it thus becomes highly 

 desirable to accelerate the operation. The perfection which subterra- 

 nean surveying has of late years attained enables the miner to 

 accomplish this object by a very interesting processs, whenever the 

 workings of the mine have advanced near the spot where a shaft w 

 required. The site of the shaft having been fixed upon and marked 

 out at the surface, the miner, by a series of very accurate measure- 

 ments of the length, windings, and direction of the levels, is enabled to 

 ascertain correctly their relative position with regard to this spot, and 

 consequently at what point each of them approaches nearest to a 

 supposed vertical line penetrating the rock below it. This being 

 ascertained, it is evident that by pursuing the same process still 

 further, he may determine in what direction and to what distance 

 crews-cuts must be driven from each of these points, in order to bring 

 him exactly to this line, or underneath the site of the shaft; and 

 having arrived there, that excavations exactly corresponding with it, 

 both in form and dimensions,may proceed simultaneously both upwards 

 and downwards from each cross-cut, while the shaft itself is being sunk 

 from the surface, the work thus proceeding from several different 

 points at the same .time, as shown in Fig. 3. It is found in practice 

 that the various separate portions may be made to unite with surpri- 

 sing exactness ; so much so, that even in very deep shafts, when com- 

 plete, daylight may be seen from the bottom ; and from the great 

 saving of time which the process effects, it is now frequently used in 

 mines of great depth, the working of which is much facilitated by it, 

 as the work of many years may thus be brought within the compass of 

 one or two. A very remarkable instance of a deep shaft being thus 

 sunk from several points at once occurred at the Consolidated Mines 

 in Cornwall, about thirty years ago, where a perpendicular shaft, 204 

 fathoms in depth, was completed in less than a twelvemonth, King 

 worked from fifteen different points at once. 



Flf . 3. Cron Mellon, (bowing tin- progren of a iliaft ttorlrd a 



: rill. 



As the working of a mine proceeds, the increase of shaft < and level* 

 tends to obliterate, in a great degree, the uniformity and simplicity oi 

 operation" which were at first apparent, the position of these works 

 being entirely regulated 1 y the irregular distribution of tin- productive 

 part* of the vein, as developed in their progress. When i!n- depth 

 becomes considerable, many of the first shafts are r.-n,l. . ,.! in n great 

 meMura useless, either from being inclined, and thus inconv* < 

 machinery, or from h i\ ing p i--.-d through the vein at a shallow depth 

 and thin, requiring long cross-cuts previous to commencing the <l > | i 

 level*. Hence, in very deep mines, a double tin.- !' - lulls will often 

 be found to range along the course of the prim-l|al veins ; am 1 

 tines even three shaft* will be found opposite each other, and inter 

 Meting the me part of the vein successively at greater depths. In 

 this ease, while the most recent shafts are used for drainage and ex- 

 traction, the older and more shallow ones are often fitted up as " foot- 

 ways," and serve for the. partial ascent and descent of the miner*. In 

 some of the large mint* of Cornwall it is usual to sink two shafts 

 within a few fathoms of each other, one being of large dimensions, am 

 Intended for a drainage or " engine-shaft,'' the other smaller, and adaptoc 

 to drawing stuff only. This arrangement is found more convenient 

 than having a single large shaft arranged for both purposes, for which 

 however on* shaft is often made to answer, being divided down tin 

 middle by Umbering, and one ride appropriated to the pumps and 

 ladders, while the other is occupied by the " kibbles " or iron buckets 

 used for drawing U ore and in many canes the rubbish, when the 

 Utter cannot be conveniently disposed of underground. 



Shafts in this country are generally mink of a rectangular form 

 except in our coal mines, where a circular form is often preferred. 



Those intended for the extraction of ores, or whim-shafts," are com- 

 monly six feet by four ; those employed for drainage, or " engine- 

 shafts," as they are generally termed, vary from about six feet by eight 

 o eight by ten, or sometimes are rather larger. In coal-mines the pit* 

 are generally about seven or eight feet in diameter, the dimensions 

 varying according to the nature of the ground and the arrangement* 

 >roposed in them. 



As veins are generally found to run nearly parallel, and often at no 

 ;reat distance from each other, and as the neighbourhood of a productive 

 vein is a favourable indication of the contents of others in its vicinity, 

 transverse levels or " cross-cuts " are frequently driven from mines at 

 various depths, with a view to discovering side-veins, or making trial 

 of branches which diverge from the main lode. Should a prod- 

 vein be found in the neighbourhood of the first, the most usual mode 

 of working it is by extending levels upon it, at the same depth a 

 in the mine from which the cross-cuts are driven, commencing at tin- 

 points where these intersect it. In thin cose the same shafts will 

 probably serve for both the old mine and the new one, the on. 

 in fact, a mere appendage, as it were, to the other. Should the distance 

 of the newly-discovered vein be considerable, it will prevent the workings 

 from being carried ou in this mainn-r. Imtli from the length of tin- 

 cross-cuts, and from the difficulty of \i-i ; il iti,.n and extraction ; and it 

 will therefore be necessary to sink nhafU upon it, and lay it open as a 

 separate mine, in a somewhat similar nianm-r to that which has already 

 been described. 



Metalliferous veins ore often traversed by other veins crossing tlu-in 

 nearly at right angles, which seldom contain ore, excepting perhaps 

 near the points of intersection : they are termed " cross-courses," or 

 " cross-veins," and occur in most mines. Cross-cuts are sometime! 

 carried upon these veins, portly to explore their contents, ami ]uirtly 

 because the work will often proceed more rapidly than when in the 

 solid rock ; but this is not considered eo effectual a mode of i-\; 

 the ground and discovering new veins as by driving in the rock i' 



The intersections of veins are very generally accompanied by a shifting 

 and di-rangemont of the metalliferous vein, the two portions of which 

 on the opposite aides of the cross-vein, ore often separated to a very 

 < -onsiderable distance. As veins are most productive at or near the 

 points where such intersections occur, the metalliferous mass on which 

 the miner had previously been working is completely lost on coming to 

 a cross-vein; and it is frequently a work of considerable dime i. 

 recover it again, as the productive vein may be thrown or " heaved " 

 completely out of iU former course. The first object to be ascertained. 

 in the search for the dislocated vein, is in which direction the " 1. 

 has taken place, whether to the right hand or the left ; and from analogy 

 the miner is generally, though not always, enabled to form a . 

 judgment on this head. He then continues the level u] . 

 vein in this direction, till the metalliferous vein is again nut v. ith n 

 the opposite side, when the level is continued upon it as befoi 

 the search should be continued for a long distance without success, 

 he will drive in the other direction, in expectation of meeting with it 

 there, 



Aditi. Where a vein has beon worked by driving n level tow; 

 from a valley or other convenient point on the surface, the iliah 

 the point of intersection is, of course, complete; and hence in mount 

 ainons countries, where deep ravines occur, levels maybe l>n: 

 one below another, so as to prove the veins and unwaU-r 1 1, 

 considerable depth, almost superseding the use of machinery tor thi 

 purpose. Levels thus opening t<> the surface, and serving i 

 are termed "day-levels " or "adits," and few mines are without one. In 

 cases where mines have been opened by sinking down from the - 

 which is the most common method, an adit is general !\ 

 from the bottom of some neighbouring valley (sec /'//. -_M, v. 1 

 towards the vein with a slight inclination, so that tie 

 may readily flow through it ; and in largo mining districts adits have 

 been formed of enormous length, traversing a considerable number of 

 mines, and carrying off the water to the lowest practical >le | 

 drainage. In driving an adit, if the length l.e e.,n 

 reaches the mine which it, is intended to dr.tin, the distance i 

 divided into two or more portions by sinking shafts upon 

 and driving from the bottom of each on reaching the requisite depth. 

 The work is thus expedited in proportion to the nuinUei of p,.im, 

 from which operations may be commenced. Adits may often l.e made 

 valuable as works of discovery, by making them cross the . 

 the veins occurring in the district, so as to intersect them in their 

 course, wheu they afford the means of trial at a cheap rate, l>y driving 

 upon them at the points of intersection. In some cases adits may 

 be carried almost entirely upon veins, to which they thus afford an 

 important trial. 



It is evident that the shaft* and levels may be indefinitely extended 

 in the manner which has now been pointed out, and should the produce 

 of the mine be considerable, the portions of the vein successively laid 

 open continue productive, and otlnr veins be discovered by cross- 

 cutting in iU vicinity, this extension of the works may be continued 

 for many years. Thus, in the course of time, from a few niniplc 

 excavations, we obtain that almost infinite complication . f shafts, 

 levels, cross-cuts, and other workings, which characterise the workings 

 of an extensive mine, with, all its numerous appendages of pumps, 

 machinery, and buildings. 



