PART 3.] Foote ; Geological features of the Madura district, 8gc. 
157 
often f^ovei'ed with light wreaths of grit and sand collected by the prevailing 
winds. 
The red soil is the more common form, hut both it and the yellow variety 
show frequently on the hardest parts of the surface a semi-metallic-looking 
blush of bluish-black color. 
Over the lateritic bands the soil is generally a nearly pure, less frequently 
somewhat clayey, sand. 
Real blown sands were very rarely noted within the limits of sheet 80 as far 
as the survey extended ; those in the little strip of coast examined in the Adram- 
patam corner of Palk’s bay are hardly -worth noticing, and the same may bo 
said of a few low hillocks on the hank of the Vaigai river near Tirupavanam 
(Tripj)awanum). The most notable accumulation of sand raised by wind was 
seen between Vadakur (Vuddacoor) and Pinneyur, thi’ee and half miles south¬ 
west of Ortendd Chattram (Mootooaumaulpooram of the Atlas map). The 
hillocks here are of very small extent, but rise from 15 to 16 feet in height; 
they are limited to a very small superficial area. 
Economic Geology .—Pew districts even in the poor region of Southern India 
are so extremely destitute of valuable minerals as the country dealt with in those 
pages. Building-stones, road-metal, and kankar for lime-burning are at present 
about all the material collected for economic purposes, with the exception of a 
little impure salt and saltpetre. 
Iron used to be smelted in some quantity from ores obtained from the 
lateritic conglomerate beds as testified by the quantities of iron slag scattered 
over the country and here and there accumulated in largo heaps. Of late, how¬ 
ever, this industry seems to have died out entirely, for I could not hear of its 
being now followed anywhere, nor did I come across any villages in which smelt¬ 
ing furnaces were still in operation. 
The compact richly ferruginous laterite conglomerate furnishes endless mate¬ 
rial for rough building purposes, and is even carefully cut and dressed foi- better 
class buildings now put up at various places by the rich Natukotai Chetties, a 
caste of rich traders and soucai-s who are buying up much land in many villages 
on the lateritic area and building palatial houses in every direction, besides tanks 
and temples. Many old buildings of importance have been built of this stone, 
e. g., the great fort at Kilanelikotai and the fort at Arrantangy. The laterite 
of the Shenkarai patch and the northeim part of the Shahkotai patch yields the 
largest and apxjarently the most reliable and homogeneous blocks I have seen 
quarried anyv^here between Cape Comorin and the Kistna I’iver. 
Of gneissic rocks the Puliarputti banded gneiss is the most largely used. The 
great quarries four miles east of Tripatur are largely worked for blocks of all 
sizes, up to nearly 30 feet in length. The stone is in great demand because of 
its beauty and moderate price owing to its being easily quarriable. Large 
pillars about 12' by 3' by 1' 6" roughly dressed for the gates of pagodas or man- 
tapams cost only Rs. 30 on the spot. 
Very handsome granite gneiss is quarried at Tirkonum, west of Pudukotai, 
and at Kunamulla trigonometrical station hill, fourteen miles to the north. 
The gi’anite gneiss at Virallimallai, twenty miles south-west of Trichinopoly 
