DESCRIPTION OF THE PRINCIPAL EXPOSURES. igi 



undulations of the plateaux facilitate the production of lakes of 

 considerable dimensions with very slight artificial assistance. At 

 Ootacamund on the Nilgiris, at Yercaud on the Shevaroys, at Kodai- 

 kanal on the Palnis, and at Neuralia and Kandy in Ceylon, lakes cf con- 

 siderable size have been formed by taking advantage of the facilities 

 offered by the gently undulating surfaces of the plateaux formed of 

 the rocks which are grouped together in this series. 



The Palnis are physically connected with the Anaimalais 

 and are probably also geologically a continuation of these hills; but 

 this area lies principally in the Coimbatore District and is only 

 now in the course of being surveyed. 



Our principal information concerning the distribution of 

 this series in the remaining portions of Madura and Tinnevelli is due 

 to Mr. R. B. Foote, 1 who described the leading member of Jthe series 

 as a " granitoid gneiss " t which, from its occurrence near Cape 

 Comorin, was designated the " Cape Comorin type" ( Op. cit. y 



P . 28). 



The "Cape Comorin granitoid gneiss" appears to be inter- 

 Cape Comorin type of banded with granular quartz rock, and in the 

 Madura district these rocks, according to 

 Mr. Foote, form six distinct groups, associated in a few places with 

 coccolitic marbles. In the Tinnevelli District both the granular 

 quartz rock and the crystalline limestone are found again in associ- 

 ation with the Cape Comorin type of granitoid gneiss. 



Many of the prominent hills in these two southern districts 

 are composed of the charnockite series (" Cape Comorin type 

 of granitoid gneiss"). The southern ghats, which are partly 

 included in the State of Travancore, are practically composed of 

 these rocks, Mahendragiri, the most southerly of the great peaks 

 of the range, being a noteworthy example, attaining an altitude of 

 5,419 feet. 2 



1 Mem. Geol. Surv. Ind., Vol. XX, p. I. 



3 For further details concerning the crystalline rocks of Travancore see W. King, Rec. 

 Geol. Surv. Ind., Vol. XV, p. 87, and Foote, Ibid, Vol. XVI, p. 20. 



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