MINING. 113 
two platforms which serve for boring the hole and firing the charge; p is a 
piece of stone which prevents the wedges and rod from being thrown too 
far when the blast is made. 
Another mode of detaching portions of a rock or bed is by kindling fires 
on the mass to be operated upon. This mode is used where fuel is cheap and 
the rocks are not well situated for drilling. The portions of rock detached 
by the fire may be easily removed by the pickaxe or crowbar. Pl. 25, fig. 10, 
represents the working of the mine in the above manner at Felsé-Banya in 
Hungary. Preparations are made for working the mine by driving levels, 
which lie nine fathoms below one another, and are connected by shafts and 
winces. Piles of wood are erected on the bottoms of the levels, the whole 
length between the shafts, in order that the fire may operate on the roof of 
the levels. If the level is so high that the flame from combustibles placed 
on the floor will not reach the roof, a wooden platform is built up from the 
bottom of the level and covered with stone to protect it from the fire, upon 
which the piles of wood are placed. The platform is gradually raised as 
the roof is mined away. 
8. Minine At THE SURFACE. 
In many cases the best mode of working beds of minerals is to take off 
the roof of sterile materials which covers the bed, and to work them under 
the open sky. Such is the case with respect to beds of peat, many stone 
quarries, beds of bog iron, and in some cases mineral coal. 
In general, the following rules are to be observed in mining under the 
open sky: In the first place, a sufficient portion of the bed or vein to be 
mined must be laid bare, in order that the materials to be dug out may be 
easily procured. We must then descend as far down to the lower part of 
the bed as can be done without threatening the caving in of the walls. 
Secondly, we must provide the means of containing water if it collects on 
the bottom of the mine; all the water should be collected at one point, 
where the pump is placed. Thirdly, after the first bank or step is wrought 
out we go on to the next, taking care that a drain is left under the rubbish 
of the first step to carry off the water. JF ourthly, the general rule is to 
commence at the lowest point in the bed and carry on the mining from 
below upwards, by cross-cut on the longer line of the bed. 
As an example of mining at the surface, we will here give a plan of the 
operations at the slate quarries near Angers in France. These quarries lie 
east of that city, on a series of beds of slate which have an average extent of 
two to three miles, and run in a direction about twenty degrees north of west. 
In the year 1841, 14 quarries were being worked, with a yearly production 
of about $4,000, 000. The beds dip almost meatier but usually a few 
degrees to the wel (pl. 23, fig.6D). The separation coincides with the 
stratification, as the fakeaved impressions of organic remains which are 
found abundantly between the layers show. 
The slate quarries belong to different companies. The operations of each 
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