145 
PART 3.] Foole: Geological fcalam of the Madura List rid, l^-c. 
outcrop and along tlie plane of an important joint occupying a nearly hori¬ 
zontal position, giving rise to numerous low caves and rock-shelters which are 
yet used for various purposes by the field labourers. The basset edge of the 
bedding coincides with the run of the hills, and the dip is westerly. A good 
specimen of a rock-cut Hindu temple is to he seen on the east side of Hartha- 
mallai, and near it ai’e some large holes, now full of water, formed apparently 
by the weathering out of lenticular masses of more perishable rock. 
* The Annavassel hills are of very similar petrological character, and so also is 
the bold rocky mass of the Kudumimallai (Kodcmeahmallai), four miles further to 
the south-west, so called by the natives from a fancied resemblance to the lock of 
hair worm by orthodox Hindus at the back of their heads. 
These hills are almost bare of vegetation owing to their very rocky character, 
but to the east of Narthamallai is a ridge of the highly crystalline quartzose rock 
above mentioned, which crumbles by weathering into a coarse grit thickly covered 
by heavy thorny scrub. Very little rock is to bo seen here, and the contrast 
between the two ridges is very marked. The bedding of this quartzoso rock 
is very obscure, but still traceable by the lines of hrematitic grains which 
form discontinuous laminm. A precisely similar rock, probably the extension of 
the same bed, is to be seen a little south-east of Pilliur (Pilleoor), eleven miles 
to the north-east-by-north. Ho other minerals could be traced in this rock. This 
band of granular quartzose gneiss shows also strongly to the east of the Anna- 
vassel hill, and is doubtless connected with more southerly outcrop of similar 
rock, as, for example, that on the south bank of the Vellar, close to Henianur. 
Still further south this very peculiar variety of gneiss occurs largely, and forms 
several low hills and ridges which, though nowhere of any height, are yet con¬ 
spicuous from their light color where not covered by jungle, or from their being 
crested by narrow ridges of bold blocks and tors. Among these the following are 
noteworthy: the Heddamurrum hill, three miles north-east of Tripatur, the 
Manmallai (Miinmullay), the north-eastern extremity of a long low ridge which 
crosses the Tripatur-Sivaganga high road, and may bo traced for some thirteen 
miles to the west-south-west. This, which in parts is crested by a row of striking 
tors, forms for a distance of fully ten miles a perfectly straight boundary line 
on which the western edge of the Sivaganga (Shevagunga) lateritic patch abuts. 
Another ridge, about 250 feet high and three miles long, lies between two and 
three miles north-west of the Manmallai, and is locally known as the Yerimallai. 
In both these ridges the beds have a very high westerly dip, ranging from 75“ 
to nearly, if not absolutely, vertical. Very similar to both these ridges is another 
which abuts on the left bank of the Vaigai river, about four miles south-east of 
the town of Madura, and which extends east-north-east towards and apparently 
joins the row of huge tors which culminates in the Trivadur trigonometrical 
station hill. Besides the outcrops of the granular quartzose gneiss above men¬ 
tioned three other occurrences of it should be noted ; these are a band occuning 
about two and a half miles east of Tripatur, which is possibly a continuation of 
the Heddamurrum beds before referred to. The gneissic rock seen in the inlior 
south of Trimiem is a similar granular quartzose variety, the crest of a basset 
edge from which the overlying laterite has been denuded. 
