258 
LATERITE FOUND IN VARIOUS PARTS OF INDIA. 
the red hills at Madras, Nellore, Singhiri- 
tunda ; in the two latter on granite : he ob- 
served in it plumb blue lithomarge, and pisi- 
form iron ore- The origin of this rock may 
therefore, in Cole’s opinion, be attributed to 
the basalt and to the wacken,not only in the 
Hydrabad country but in three other locali- 
ties, where the mineral is said to prevail 
closely resembling that near Hydrabad, which 
is his authority for considering laterite as as- 
sociated with the trap formation. Captain 
Coulthard talks of the iron-clay in the 
Saugor district. The Rev. R. Everest, in 
the Gleanings of Science, alludes to having 
seen the laterite. Mr. Malcolmson states that 
the Indoor and Nirmal magnetic iron rapidly 
becomes red on exposure, and the rock, on 
being broken and the ore separated by wash- 
ing, leaves a reddish clay. Veins of quartz 
pass through the granite and sometimes con- 
tain magnetic iron. The laterite of Bederis 
found on granite, and hot springs, and hills 
capped with trap, are found not far off. Mr. 
Malcolmson did not believe that any orga- 
nic remains had been found in the laterite. 
Mr. Cole says that there is no reason to 
doubt that the laterite is a mechanical 
deposit, composed of the debris of older 
rocks. 
We proceed to notice his account of the 
mineral in the vicinity of Madras. The Red 
Hills and Gundy are the only localities in 
its immediate vicinity, where he was able to 
discover the laterite. Nearer than the spots 
alluded to no hillock arises to break the level 
uniformity of the plain, on which Madras 
and its widely scattered gardens are spread 
out. The Red Hills are situated eight miles 
north-west of Madras ; they are mere un- 
dulating ground, scarcely of appreciable 
elevation above the surrounding country, the 
highest eminence not attaining a greater 
elevation than fifty or sixty feet above the 
level of the plain. The whole laterite for- 
mation occupies a triangular area of about 
fifty square miles, extending nearly ten miles 
to the westward of the gravel pits on each 
side. Mr. Cole has explored an area of this 
extensive part from three to four square 
miles. Line of bearing of undulations irre- 
gular ; direction south-west to north-east. 
“ From these rising grounds the land des- 
cends to what is termed the Lake, which is 
bounded on three sides by the eminences de- 
scribed above, the waters (when there are any) |j 
being confined, on the greater portion of the lii 
eastern side, by an artificial embankment, or j; 
Brnid, but for which there would be no lake | 
at all, as the country descends on that side |: 
towards the sea, it is believed about two and 
a half feet per mile. To the north east a 
natural drain for the waters from the higher I 
grounds existed, but it has been filled up, at ll 
the place of junction with the lake, by a dam | 
and wmter sluice, after the manner of an ordi- i 
nary tank, for the irrigation of the country- ( 
The old channel, however, remains, and the i! 
banks, in some places fifteen feet high, show !! 
the mineral structure of the spot. They are I 
composed of a dark ferruginous stone, ar- ;[ 
ranged in a stratiform manner, presenting 
seams or partings, two or more feet asunder, j| 
parallel to each other, and nearly horizontal. ! 
Vertical fissures intersect the seams at right i 
angles, and thus produce prismatic masses of j 
the rock, which give these natural walls some - 
thing of the semblance of huge artificial i 
masonry. On breaking into the interior of , 
these masses, the rock is palpably a conglo- 
merate. Nodules of various sizes are ob- 
served, imbedded in a elayey paste, which is 
very hard and tenacious. These nodules may i 
be picked out, without much difficulty, when I 
it evidently appears that they are water-worn i 
pebbles, presenting considerable angularity [ 
of STirface, yet still sufficiently rounded to ! 
indicate their having undergone attrition, , 
most likely by the turbulence of an inunda- j 
tion, which bore them away from their ori- i 
ginal position as parts of a solid rock, and | 
deposited them, in their present conglomerate I 
form, with the mud which now agglutinates ! 
them. 
The nodules are observed of all dimensions, j 
from the size of a filbert, to masses a foot or : 
more in diameter. Their fracture exhibits ! 
the structure of a coarse-grained sandstone, j 
or grit, of a deep chocolate, or claret hue 
(No. l).* This nodular sandstone is made i 
up of fragments of quartz (some rounded, but J 
for the most part angular), from a minute i 
sand up to the size of a pea. Added to the , 
quartz, there are occasionally found small | 
masses of a white earth, like lithomarge, 
appearing to be felspar in a state of decom- ! 
position (No. 2). This is found in small i 
nests, here and there ; but I have no doubt i 
that a good deal, minutely subdivided, went 
to form the paste whieh united the parts of 
this conglomerate together. Thirdly, mica 
is found a constituent of these sandstone 
nodules, in very minute scattered leaves. 
This sandstone precisely resembles the 
specimen from Puddayarara, near Samul- 
cottah, in the Northern Circars, deposited in ^ 
the Mineralogical Cabinet of the Madras ' 
Literary Society, by Dr. Benza, who has I 
thusdescribed its structure and relations in the ; 
* The Numbers refer to specimens pre- 
sented to the Society, in illustration of the 
Paper. 
