Chap. XXXVIIL] 
SANDUR STATE. 
1007 
average angle of about G5°, and possessing a thickness of not less than 
AB, or about 90 feet. The outer or lower boundary of the bed was 
seen in the face CD, where the manganese-ore seemed to rest upon a 
few feet of iron-ore and this upon soft white lithomargic rock, the 
whole being apparently confc rmably bedded ; but the inner edge of 
the supposed bed was not exposed, being covered by the lateritic 
rock. Hence 90 feet is only the minimum thickness of this apparent 
bed. To test the continuous-bed hypothesis Mr. Ahlers drove the 
tunnel DE into the working face below the level of the base of 
the manganese-ore in the face CD. I was driven in a total horizontal 
distance of 66 feet, with a total rise of 20 feet at the inner end, and 
had the ' bed ' been continuous should soon have cut the manganese- 
ore. But, except for a few tiny segregations of manganese-ore, and 
veinlets of limonite, it showed not a trace of either manganese- or 
iron-ore. Instead of this it was all the time in variegated banded 
lithomargic clays, which did not have such a steep dip as the 
manganese-ore ' bed ' on the outcrop. My explanation of this 
phenomenon is shown in the section in figure 76, in accordance with 
which I suppose the mangan?se-ore deposit to have been formed at 
the surface by replacement, either of the clays or of the rocks of 
which they are the alteration products, by manganese oxides deposited 
from percolating waters. I must say that Mr. Ahlers had already 
come to this conclusion before I visited the place, and that we agree in 
a general way as to the origin of these manganese-ore deposits The 
evidence of the two other deposits that have been opened up, namely 
Sannasil ilaruvu and Rstmandrug No. 4, point to the same general 
conclusions as to the origin of the ores. 
We can now consider this theory in more detail. Many interesting 
. 1 .X sections are to be seen in thi road-cuttings on 
Kviaence supporting the o 
superficial repliieeiiieiit the ghat road leading down from Ramandrug 
^^T^hJ Nan'iyiindevaikeira to Narayandevarkerra, a village in the plains 
Ghat Sections. ^]^g ^gg^ Sandur synclinal. At 
many places on the way down are to be seen sections showing 
nodules of manganese-ore in the altered phyllitic rocks. They are 
usually of ovoid or flat lenticular shape, a few inches long, with 
their length parallel to the cleavage and bedding — which are usually 
coincident — of the rock. From these nodules small stringers of 
