

158 HOLLANn: GEOLOGY OF THE NEIGHBOURHOOD OF SALEM. 



stayed 20 days and gave a brief account of the hill tribes, the Todas, 

 Kotas and Badagas n (IX, 257, 258). 



On the return journey to Pondicherry he visited the mine from 

 which aqua-marines had been obtained. The mine had been leased 

 to Mr. Heath, Commercial Resident, and was situated at Pataly, 22 

 lieues (53 miles) south-west of Salem. The vein in which the aqua- 

 marines were obtained measured not more than one foot in thickness 

 and was enclosed in a handsome pegmatite at about 15 feet below 

 the soil, the water which abounded in the pit made the exploitation 

 a difficult matter : the aqua-marines were considered by Leschenault 

 to be superior to those of Siberia. 24 



In September 1819, Leschenault started for Bengal, returned to 

 Pondicherry in January 1820, and started in April of the same year 

 to explore the south of the Indian Peninsula and Ceylon. 



23 Although no mention seems to have been made of rocks collected on his way 

 to Coimbatore and the Nilgiris, he must have met many exposures of, amongst 

 others, the pyroxene-granulites which are the most abundant rocks in the 

 Nilgiri hills. It is not unlikely, too, that he must have known of the crystalline 

 limestone, 6 miles south of Coimbatore, much of it being used for building 

 purposes in the town. This crystalline limestone agrees in many respects with 

 those described by Lacroix and is also associated with scapolitic rocks. 



In the journey from Trichinopoli to the Nilgiris, via Coimbatore, Leschenault 

 probably crossed the crystalline limestone bands near Koolitalai (io° 55'; 78 29') 

 and passed by road through Karur (io° 57' ; 78 o/), Paramatti (io° 57'; 77 58'), 

 Vellakovil (io° 56!; 77 45'), and Kangayam. 



24 Paitalai 'Coimbatore District Man., 1887, pp. 23 and 443), is about 7 miles 

 north-west of Kangayam in the Coimbatore district, and between 50 and 60 miles 

 south-west of Salem. Tie pit from which the aqua-marines are said to have been 

 obtained is still pointed out; large veins of graphic pegmatite are seen to cut 

 through mica schists, and many of the pegmatite fragments on an adjoining 

 rubbish heap are seen to contain several well-crystallized minerals such as 

 garnet, albite, etc. : the aqua-marines were probably found in such drusy cavities 

 of the coarse-grained, miarolitic rock. These pegmatites cut the micaceous rocks 

 in all directions, and have no known genetic relationship with the pyroxenic and 

 other gneisses described by Lacroix (Rec, Geol. Surv., Ind., XXIV, 170). The 

 whole area in the neighbourhood of Pattalai is geologically complicated: about 

 3 miles to the south-east there are large masses of an elseolite-syenite containing 

 graphite, and associated with augite-syenite and felspar rock containing 

 corundum. To the north-west there are pyroxenic and hornblendic gneisses 

 associated with quartz iron-ore rocks. 



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