Chap. XXXVIII.] sandur state. 1015 
below, the mark. This can only be shown in years to come as the 
deposits are further opened up. 
Considering the enormous quantities of manganese-ore that must be 
allowed to be present in these hills even on the 
Arc the quantities of ore . . , , 
too liuge to have been most Conservative estimate, one cannot help 
formed by superficial re- wondering if the mode of formation ascribed 
placement. ° 
to them above is adequate to account for their 
accumulation. It must be remembered that even if we allow — simply for 
the sake of argument, and probably much overstepping the mark — that 
the manganese-ore deposits of this State contain in all 100,000,000 tons 
of ore, and that the average manganese contents of the ore is 50 per 
cent., which also oversteps the mark, so that we allow 50,000,000 tons of 
manganese to be present, yet this forms a very small proportion of the 
whole of the mass of rock composing these hills. Thus, one cubic mile 
of rock alone, of specific gravity 2"7, would weigh 11,090,000,000 tons; 
so that, even if all the manganese had been derived from a cubic mile of 
rock only, it would correspond to 0'45% only of manganese in the 
original rock. Now the average amount of manganese in the earth's 
crust is usually taken as about 0"08. If the whole of the 50,000,000 
tons of manganese had been derived from 6 cubic miles of rock only, it 
would correspond to only 0'075% manganese in this rock But 
there are many times this amount of rock in the Sandur Hills ; and 
even though the solutions producing the surface replacements did not, 
in all probability, draw on nearly the whole of this rock for their 
manganese, yet it will be seen that the amount of manganese in the 
fresh rocks must have been amply sufficient to give rise, by the process 
of secondary replacement, to the manganese-ore deposits we now find. 
It is further to be remembered that the rocks with which the manga- 
nese-ores are associated were probably more or less contemporaneous in 
time of formation with the manganese-bearing rocks of the Centra] 
Provinces. And it may easily have happened that at the same time as 
there was a great precipitation of manganese oxides taking place in the 
Central Provinces and Central India, the deposits being formed in other 
Dharwar areas, although not sufficiently manga nifero us, except perhaps 
in rare cases, to be called manganese-ores, were yet often more highly 
manganiferous than usual. So that if it be considered that an average 
amount of 0'08 per cent, of manganese in the rocks of Sandur would 
