544 



J. G. Malcolmson, Esq., on the Fossils of 



localities, that sulphur is manufactured from it. At Jumulmudagoo I found the 

 limestone interstratified with muriate of soda ; and it is therefore probable, that 

 the salt diffused through the alluvial soil so extensively as to render the water 

 of the Pennar brackish during the hot season, and the inhabitants independent 

 of the sea-coast for a supply of that article, is derived from this source. 



On emerging from the gorge in the Nulla Mulla range, the Pennar enters 

 the plains of the Carnatic, and near its mouth flows through low hills of late- 

 rite. This deposit rests on the ordinary granite of the Carnatic, with its as- 

 sociated sienites, hornblende schist, quartz rock, and mica slate. It is in a 

 rock composed of a mixture of the last two minerals, that the copper-mines of 

 the Nellore district are situated*. In the same neighbourhood, the sandstone 

 and argillaceous limestones are little elevated above the sea, and are con- 

 tinuous with the same rocks on each side of the Kistnah. They are broken 

 through by insulated basaltic hills, in the neighbourhood of which subterra- 

 nean sounds and frequent local earthquakes are reported to occur; an asser- 

 tion I am the more inclined to believe, having myself experienced two slight 

 shocks during a casual visit to the district. 



Havingbriefly described some of the more remarkable phenomena exhibited 

 by the southern portion of the great sandstone and argillaceous limestone 

 formations, it will be unnecessary to enter into any detail when we meet with 

 the same rocks to the north of the Godavery in connexion with the fossil 

 beds discovered in the great basaltic district. 



Granite Platform between the Kistnah and Godavery. 



(See Map and Section I.) 

 With regard to the granitic platform of the Deckan, which intervenes be- 

 tween the Kistnah and Godavery, much accurate information is already before 

 the public ; it will therefore be necessary only to observe, that it is intersected 

 by numerous greenstone dikes (sometimes of greenstone porphyry), having 

 for the greater part a direction from S. by E. to N. by W., and not very dif- 

 ferent from that of several of the ranges of basaltic mountains to the north. 



These dikes, and the detached masses connected with them, are entirely composed of a crystal- 

 line compound of hornblende and felspar, without distinct crystals of augite; and I have never 



* The ores are of various kinds, but the richest is a sulphuret, containing, according to Mr. 

 Prinsep, 69 per cent, of the pure metal. The copper also occurs in a slate which Mr. Oucter- 

 lony, of the Madras Engineers, informs me, was considered in Cornwall to be identical with the 

 Killas. If this slate belongs to the " argillaceous limestone" formation, the fact will be of use in 

 determining the relations of that rock to the gneiss, talc slate, and mica schist ; a subject on which 

 no observations of any value have yet been made. The primary rocks of this district contain 

 magnetic iron ore and corundum, both of which occur in the diamond sandstone. 



