558 
MA>-GA>-ESE DEPOSITS OF IKDIA : klNING. [PaBT III 
deposit, it would probably not pay to remove more than one or two 50- 
foot slices in the way ilhistrated in figure 30. If the ' country' were very 
sound and tough, it would probably be cheapest to remove the top 100 
feet of the ore by means of an open quarry, as indicated in figure 31, but 
less wide,, and then to drive in tunnels along the strike of the ore-band at 
the 20C-foot and 300-foot levels respectively, and to fixst stope out the 
ore from the 200-foot level up to the 100-foot level, removing the ore 
through the 200-foot tunnel, and to treat the next slice in the same way, 
removing it throiigh the 300-foot tunnel. [During 1907 a beginning has 
been made to mine in this way the portions of the Mansar deposit lying 
below the 100-foot level.] These tunnels woiild also serve for drainage. 
In the exceptional case of the ore-band not running the whole length 
of the hill so that it did not crop out at the two ends, it might be 
cheaper to drive the cross-cut tunnels B, C, and D, as in figure 31, 
instead of tunnels on the strike. If, however, the groimd were very 
soft and decomposed it might be easier to continue the quarrying system 
as indicated by the stepped lines, representing successive stages, down 
to the base of the hill. Arrangements would have to be made for 
draining the quarry, probably through the two ends of the ridge. In 
fact the free drainage of the deposit could to a certain extent be 
secured by working the ends of the ridge quicker than the middle and 
so keeping them at a lower level. But whether the ore down to the 
base of the hill were quarried or mined there is no doubt that mining 
would have to be resorted to, in order to follow it any deeper, should it 
continue. 
It is, of course, only if the ore-band were fairly thick that it could pay 
to quarry the deposit by removing the whole 
Thin ore- baud in a hill. . ^ . ^ „X i i- -j 
SIX suces as m figure 30, or by makmg a wide 
quarry, as in figure 31. If the ore-band were thin, say only 5 to 10 feet 
thick, then it would probably be found that the only economical way of 
recovering all except the top 50 feet would be by mining the deposit 
like a mineral vein, as indicated in the previous paragraph for the 
case of a steeply dipping band of considerable thickness, with sound 
' country '. 
We now come to the case illustrated in figure 32 of a fairly thick 
ore-band, the outcrop of which is on low ground. 
ouro?Tow^^ound^^'°^ this case it does not make much difference 
whether the angle of dip of the deposit is mode- 
rate, as represented in the figure, or whether it is steep, say from 70'^ to 
