488 PEOCEEDINGS OF THE GEOLOGICAL SOCIETY. [June 17, 



sisting mainly of quartzite with a varying proportion of impure 

 brown haematite pellets. 



The quartzite pebbles of the laterite can easily be traced to the 

 sources whence they came, which are at no great distance off. 

 The primary source of these pebbles is to be found in the immense 

 quartzite formations capping the summits and ridges of the Naggery 

 Mountains, a group of bold detached mountains which stand out 

 between the eastern Ghats and the Pulicat lake. 



The secondary -source of the quartzite pebbles is the vast Jurassic 

 conglomerates forming the Alicoor and Sattavedu hills, two groups 

 of hills lying to the south and south-east of the jSTagari (ISTaggerj^) 

 mountains. These conglomerates are in part quite unsolidified, 

 partly also compacted into hard rocks. They have yielded an 

 abundance of already perfectly waterworn material towards the 

 formation of the much younger lateritic conglomerates. It was from 

 these Jurassic conglomerates also that the implement- makers drew 

 their supplies of pebbles out of which to chip the various tools and 

 weapons they required. 



The laterite conglomerates occur chiefly around the base of these 

 conglomerate hills, which must have stood up as islands in the 

 laterite sea, and may very likely have been the home of the tribe of 

 men by whom the implements were manufactured and used. The 

 annexed diagrammatic section (fig. 2) shows the general relations of 

 the different geological formations referred to. 



The Alicoor hills formed the most southerly source whence these 

 people could at that time obtain any quartzite ; and the number of 

 implements in the laterite decreases steadily the further you go from 

 these hills in a southerly direction. The most southerly point at 

 which I found implements was close to the Rajah's Choultry, 3| 

 miles north-east of Coujeveram. The country south of the Palar river 

 yielded no quartzite implements, though examined for them by my 

 colleague, Mr. Charles A. Oldham, a very keen-sighted and close 

 searcher. To the west and east of the Alicoor hills a similar steady 

 diminution of the number of implements, increasing with the dis- 

 tance from the hiQs, is observable. The extent of the lateritic 

 formations has been much diminished, on their western side, by de- 

 nuding agencies ; but debris of the laterite occurs scattered over the 

 gneiss rocks for many miles to the west, and may be fairly regarded 

 as the ruins of the laterite formation. Among this debris a number 

 of implements were collected by myself and by several of the en- 

 gineers of the Madras Railway stationed at Arconum. 



To the northward of the Alicoor hills the case is different ; for the 

 supply of quartzite did not cease, the main mass of the mountainous 

 coast being formed of quartzite beds for nearly 200 miles northward 

 up to the banks of the Kistna river. The conglomeratic character of 

 the laterite continues in great measure in the different parts of the belt 

 running northward through the whole length of the I^ellore district ; 

 and I collected implements at several places along this line* in 



* The systematic survey of the southern half of the Nellore district was all 



