Chap. XXVI.] 
MINING V. QUAEEYING. 
547 
or less). In fact the mining and quarrying of manganese-ore deposits in 
different parts of the world has shown that the deposits of oxide-ores 
have been formed, in the majority of cases, at or close to the surface, 
and do not extend to any considerable depth, say beyond 50 to 500 feet. 
It is to be noted, however, that if any portions of the ores of the Central 
Provinces of India can be considered as the product of the direct compres- 
sion of original manganese -oxide sediments, then such portions may 
be found to continue to as great a depth as the associated rocks of 
the gondite series, and this may be in some cases considerably more 
than 300 to 500 feet. The same remarks apply to any other deposits, 
such as those of Sweden, that have been formed by the direct compres- 
sion and metamorphism of original manganese-oxide sediments, without 
any passage through a silicate stage with subsequent chemical alteration. 
(The franklinite deposits of New Jersey in America, in which the frank- 
linite, a manganese-zinc-iron mineral, is regarded by some as having been 
formed by the metamorphism of original sediments containing both 
manganese and zinc, and which has been proved by boring to continue 
to depths of over 1,000 feet, may be cited as an example of a man 
ganese-oxide mineral proved to continue to a great depth.) 
Even on the assumption that none of the Indian deposits will be proved 
to continue to a greater depth than 300 to 500 feet below the original 
outcrop, there is still plenty of scope for true mining ; namely, between 
the depths of 50 to 100 feet and 300 to 500 feet. Before passing on to 
the next section I will state the depths to which the Indian manganese- 
ore deposits have been proved, and may be expected to continue. 
Table 87. 
Deaths to which Indian manganese -ore deposits extend. 
.\rea. 
Depth to which 
proved. 
Depth to which 
may be e.xpected 
in some cases to 
continue. 
Depth to which 
possibly in some 
cases continue. 
Feel 
Feet. 
Feet. 
Central Provuices 
80 
150—200 
.W— ."^OO, or 
more. 
Vizagapatam 
100 
150—200 
300—400 
Sandur .... 
50 
80 
100 
Mysore .... 
.30 
00 
80 
The figures given in the first columa refer only to the larger deposits. 
Ill some cases in each area deposits have been found not to continue 
even to the depths given in this columa. Those in the second column 
