304 



MINING 



workings. If a vein is intersected by transverse ones, the shafts are placed so as to 

 follow, or, at least, to cut through the intersections. When the mineral ores lie in 

 nearly vertical masses, it is right to avoid, as far as possible, sinking pits into their 

 interior. These should rather be perforated at one side of their floor, oven at some 

 considerable distance, to avoid all risk of crumbling the ores into a heap of rubbish, 

 and overwhelming tho workmen. 



With a vein of moderate width, as soon as the preparatory labours have brought 

 tho miners to the point of the vein from which the ulterior workings are to ramify, 

 whenever a circulation of air has been secured, and an outlet to the water and the 

 matters mined, the first object is to divide the mass of ore into large parallelepipeds, 

 by means of oblong galleries, pierced ten fathoms below one another, with pits of 

 communication opened up, 30, 40, or 50 yards asunder, which follow the slope of tho 

 vein. These galleries and shafts are usually of the same breadth as the vein, unless 

 when it is very narrow, in which case it is requisite to cut out a portion of the roof 

 or the floor. Such workings serve at once the purposes of mining, by affording a 

 portion of ore, and the complete investigation of the nature and riches of the vein, 

 a certain extent of which is thus prepared before removing the cubical masses. It is 

 proper to advance first of all, in this manner, to the greatest distance from the central 

 point which can be mined with economy, and afterwards to remove- the parallelepiped 

 blocks, in working back to that point. 



This latter operation may be carried on in two different ways ; of which one con- 

 sists in attacking the ore from above, and another from below. In either case, the 

 excavations are disposed in steps similar to a stair upon their upper or under side. 

 The first is styled a working in direct or descending steps ; and tho second a working 

 in reverse, or ascending steps. 



The descriptions given by Dr. Ure relate chiefly to the processes carried forward 

 in the German mines. In very many respects they resemble our own processes of 

 mining; and, for the general information these give to the English reader, Dr. Ure's 

 description has been retained. 



1. Suppose, for example, that the post N, fig. 1453, included between the horizontal 

 gallery A c and the shaft A B, is to be excavated by direct steps, a workman stationed 



1453 



upon a scaffold at tho point a, which forms the angle between the shaft and the elon- 

 gated drift, attacks the rock in front of him and beneath his feet. Whenever he has 

 cut out a parallelepiped (a rectangular mass), of from four to six yards broad, and 

 two yards high, a second miner is set to work upon a scaffold at a', two yards beneath 

 the first, who, in like manner, excavates the rock under his feet and before him. As 

 soon as the second miner has removed a post of four or six yards in width, by two in 

 height, a third begins upon a scaffold at a" to work out a third step. Thus, as many 

 workmen are employed as there are steps to bo made between the two oblong hori- 

 zontal galleries which extend above and below tho mass to be excavated ; and since 

 they all proceed simultaneously, they continue working in similar positions, in floors, 

 over each other, as upon a stair with very long wide steps. As they advance, the 

 miners construct before them wooden floors cccc, for the purpose of supporting the 

 rubbish which each workman extracts from his own step. This floor, which should 

 be very solid, serves also for wheeling out his barrow filled with ore. The round 

 billets which support the planks sustain the roof or the wall of the mineral vein or bed 





