562 
MANGANESE DEPOSITS OF INDIA: MINING. [pART III J 
the ore-bearing area, forming an enormous quarry of great depth, or to 
mine the lower portions of the deposit, driving a large number of bore 
holes to find where the ore-bodies lie. Such a process of mining 
would need very expensive timbering on account of the softness of the 
ground, and would be very uncertain, with the probability of 
leaving undiscovered in the ground a considerable proportion of the 
ore. A similar problem has arisen at Crimora in Virginia, where the 
manganese-ore occurs as concretionary nodules and pockets scattered 
through clays occupying a basin over 200 feet deep. This occurrence 
has been tackled at different times by means of shafts and open 
pits ; the former method was found to be so uncertain that it has been 
lately decided to hydraulick the whole deposit, as described on 
page 575. The Vizagapatam deposits are not however suitable for this 
treatment, in the first case because it would rarely be possible to find 
lower ground close at hand on to which the water from the hydraulicking 
could run, and secondly because the proportion of small concretions in 
the lithomarge is small compared to the more massive ore-bodies, 
which are usually of much too large a size to be amenable to 
such treatment. It might be possible in rare cases to treat Indian 
deposits by hydraulicking, but I cannot point to any good example. 
Hence it is an alternative between mining siich deposits as Kodur 
below the 100-foot level, this being uncertain as to finding all the 
ore, very expensive on account of timbering, and not improbably dan- 
gerous ; and continuing the quarrying to depths greater than 100 feet 
(a depth already reached at Kodur). It will probably be found neces- 
sary to continue the open quarry system to still greater depths than 
have at present been reached and then either to abandon the deposit or 
attempt to win as much as possible of the remaining ore by underground 
mining, at times when the market is high. 
The next case to be considered is that illustrated in figure 35. It 
represents a capping of mixed manganese- and 
Latentoid cappings. iron-ores of lateritoid aspect,i such as is often 
found in Mysore. These deposits do not continue to any depth, for they 
have been formed by the superficial replacement of quartzites and phyllites 
and pass irregularly down into these rocks through a zone of decomposed 
and partly replaced rock. The thickness (i.e., depth) of the deposits is 
1 For Ihe meaning of this word see page 382. 
