398 
MANGANESE DEPOSITS OF INDIA I GEOLOGY. [ PaRT II : 
up of these remains in their concrete matrix, by percolating waters, 
not necessarily derived from those of the present river, but more 
probably consisting of ground waters circulating before the Ganges 
happened to flow in its present channel. 
In the same way stains of manganese oxide may be found in almost 
. , . . any rock near the surface. Thus some speci- 
31 anganese -oxide staim ... 
in asbestos from Tumkliera mens obtained in opening up an asbestos 
^"^^^^^ deposit at Tumkhera Khurd in the Bhandara 
district were brought to the Geological Survey Office and were 
found to be composed of a mixture of asbestos and talc, with black 
stains of oxide of manganese in the fissures. 
Deep-sea Deposits. 
It is a well-known fact that the rivers draining off the land into the 
seas and oceans contain a certain amount of manganese salts in solution. 
The quantity, although a very small proportion of the total salts in solu- 
tion, is in the aggregate so large that, if the figures given by Sir John 
Murray be anything like correct, the amount of dissolved manganese salts 
annually carried into the sea must be equivalent to about 37,000,000 tons 
of manganese sesquioxide, Mn203, or 26,000,000 tons of metallic man- 
ganese ^ 
Before discussing the formation of the deep-sea deposits of manga- 
nese-ore I want to show that it is probable that the whole, and perhaps 
the larger part, of this manganese has not remained in solution in the 
sea-water. Murray gives the amount of manganese in river-water as 
equivalent to 5,703 tons of Mn203 per cubic mile^, and the number of 
cubic miles of river-water entering the sea every year as 6. .5243. Now 
10,000,000 years is probably a very conservative estimate of the time 
during which oceans must have existed, with accompanying land areas 
from which rivers were draining and suppl3dng water to the ocean to 
take the place of that removed by evaporation*. The present volume 
of the water in the oceans and seas of the world is given by Murray 
as 323,722,150 cubic milesS or, say, approximately 324,000,000 cubic 
1 Trans. Min. Geol. Inst, hid., I, p. 73, (1906), 
2 Scottish Ocog. Mag.. Ill, p. 77, (1887). 
3 Op. dr., IV, p. 41, (1888). 
4 We can neglec t the question of the pernianencc of the oceans ; for if they have 
not had S')mcthing like their present distribution during the whole of this time, the 
water occui)ying former oceans must have passsd from old to new ocean iire;s on the 
formation of the latter. 
6 Loc. cit., p. 39. 
