PART 1.] 
Geology of the neighbourhood of Madras. 
15 
same beds in the Alicoor hills no fossils were found. The sandstones are mostly rather gritty 
in texture and only occasionally sufficiently compact to be useful as building stones. 
Sripermatoor Group. —Appai'ently underlying these Sattavedu beds in perfect con¬ 
formity are certain conglomerates, gritty clays and shales which form the western and southern 
parts of the Alicoor hills, and which differ from the beds of the Sattavedu series in being soft 
and quite uncompacted and of white or grey instead of brown and reddish colors. Even 
the coarsest conglomerate beds at and near the base of the series are soft, the pebbles and 
boulders of quartzite and gneiss, instead of being bound together by some firm cementing 
material, merely lie imbedded in a very friable, more or less clayey, grit consisting of quartzose 
debris derived from the gneissic rocks. Flanks of the hills consisting of these uncon¬ 
solidated rocks are deeply covered by debris which is cut through by only a few rain-gullies of 
recent origin, and it is these only which afford sections of the undisturbed rocks. Many of 
the gullies, however, do not even cut through the thick coating of debris and rain wash. No 
section was found showing these unconsolidated beds in contact with the consolidated 
Sattavedu beds where they approach each other in the centre of the Alicoor hill group, but as 
far as the rounded outlines of the hills at that point serve to guide the eye there is an 
undoubted dip of the softer beds under the hard conglomerates of the Sattavedu series. No 
sign of any fault between the two series could be traced, but a fault might well exist and yet be 
perfectly masked by talus and debris. The nearest visible point of approach of the two series 
is a short narrow east and west ridge abutting at right angles against the hard basement-con¬ 
glomerate bed of the Sattavedu series, which bed here forms a prominent north and south 
ridge, succeeded to the eastward by several other ridges, corresponding to as many great con¬ 
glomerate beds. The valleys running down north and south from the cross ridge above 
mentioned are the two principal valleys in the central mass of the hill group, and the depth 
to which they are excavated is due to the greater softness of the underlying beds as compared 
with the overlying series. The southern part of the Alicoor hills, called by the natives the 
Naikenpolliam hills, is apparently' composed only of the unconsolidated beds which have trend¬ 
ed in the direction of their strike from north and south to west-north-west and east-south-east. 
The basement bed at the south-west of the Alicoor area near the village of Naiken¬ 
polliam contains included masses of conglomeratic quartzite of such tremendous size—800 
to 1,000 cubic feet in bulk—that they suggest the idea of their being the relics of the base¬ 
ment bed of the Cuddapah rocks, which are so splendidly represented about eight miles to the 
north-west in the tremendous cliffs of the Naggery ridge, parts of which have a vertical face 
of 1,000 feet high. 
Glacial agency being inadmissible in so southernly a latitude, except on exceedingly 
strong evidence, the only probable explanation remaining is the one above suggested, which 
derives great probability from the fact that, on a far smaller scale indeed, similar masses of 
gneiss are included in situ in the basement bed of the Rajmahal plant beds at Ootatoor and 
elsewhere in the Trichinopoly district. These great quartzite masses, it is true, are not seen 
to be resting on the gneiss surface, hut the latter can only be a few feet further down the 
slope. The inclusion of gneiss blocks in the basement bed of the Rajmahal series is to be 
seen only' a few miles to the south in the banks of the Naggery river at Chittapuram. 
Numerous plant remains of unquestionable Rajmahal species were found in the principal 
section at the south-west end of the Alicoor hills. Amongst these plant remains were parts 
of Tmniopteris, Dictyopteris, Palteozamia, and Pteropkyllum, and Poacites-like stalks. 
Unfortunately' from the friable nature of the clay bed in which they' occur the 
majority appear to have become unrecognizable in drying, though when freshly extracted from 
the matrix even the most delicate venations and nervures were plainly' visible. 
On the south side of the Naikenpolliam ridge the lower members only of the series 
appear to be represented; they consist of unconsolidated conglomerates of various degrees 
of coarseness, gritty sandstones and micaceous sandy shales, exposed in a few streams and 
a great many' well sections. 
The only section which yielded fossils was one on the north bank of the Naggery river 
opposite to Chittapuram, where two beds of rather friable sandstone were found to contain 
plant remains, amongst which fragments of Tmniopte.ris and Dictyopteris were identifiable. 
On the opposite side of the river in the Pyanoor area the same beds reappear, and are 
there seen to be very low down in the series, in fact only a few feet above the basement bed, 
