548 
MANGANESE DEPOSITS OF INDIA : MINING. [ PaRT III 
also apply to the larger deposits in each area, such as Kandri, Kodiir, 
Diirgjvmma Kolla, and Kumsi, typical of each of the four areas mcr,- 
tioned. The figures given in the third column may be regarded as the 
probable outside limits to which the most extensive deposits in each 
area may possibly extend- It must be remembered, however, that 
these figures are based on theoretical guesses, in the absence of any 
bore holes or shafts proving the deposits to continue to any greater 
depths than in the first column. 
2. The position of the outcrop of the deposit with regard to the 
Relation of the outcroi) * opography of the surface is also a matter of some 
of the deposit to the topo- importance. Thus it might be possible to work a 
graphy. deposit outcropping on a hill 200 feet high with 
reference to the surrounding plains, and proved by boring or other 
methods of prospecting to continue to a depth of 200 feet from the top 
of the outcrop, entirely by opencast work, given favourable circum- 
stances as to the nature of the ' country' : whilst a deposit, the top of 
which only just appears above the surface of plain country, and also 
proved to extend to a depth of 200 feet below the outcrop, could be 
worked by opencast work to a depth of some 100 feet only, except by 
carrying out an enormous amount of dead work ; in fact, except at 
enormous expense, or in most exceptional circumstances, it would be 
necessary to resort to mining to extract the second hundi'ed feet of ore. 
3. If an ore deposit extend to a considerable depth so that deep 
^ ^ mining will be necessary to win all but say the top 
100 feet of it, then the value of the deeper 
ore decides whether it will pay to follow it to this depth. It has already 
been noticed that in all probability deposits of manganese-oxide ores, with 
possibly a few rare exceptions, do not extend to greater depths than 50 to 
500 feet. And it is doubtful , considering the comparatively low market 
value of manganese-ore, whether it would pay to follow a manganese 
deposit below the depth of 300 to 500 feet, even if it continued. The 
necessary conditions for it to be workable below this depth would 
probably be that the deposit should be a thick, regular deposit of high- 
grade ore situated close to the smelting centres. But let us confine our. 
selves to ores lying at depths less than this 300 to 500 feet. It is obvious 
that the average quality of the ore would have a considerable bearing 
on the possibility of extracting that portion lying at depths greater than 
50 to 100 feet. Thus near the suiface with favourable conditions it 
might easily be possible to extract ore of very low grade, say 20 to 30 
per cent, of manganese, and treat it mechanically so as to concentrate 
