204 
[yOL. XIT, 
liecords of the Geological Survey of India, 
of ferruginous gravel and clay binding the 'vvliole into a semi-compact conglo* 
mcrate, which is tho general character of the lateritic beds further north round 
the base of the Naikenpalem, Ahknr, and Sattavedn hills, tho coarseness of the 
included shingle and the amonnt of fen-nginons cement associated with it being 
locally of variable quantities. Where the shingle, which consists almost entirely of 
quartzite, attains a great degree of coarseness the ferruginous matrix is often masked 
to a very great extent, the peculiar vermicular cavities so characteristic of non- 
conglomeratic laterite are never seen, and the correlation of the two varieties as 
members of one and the same geological formation is made entirely upon strati- 
graphical grounds. 
The principal lateritic areas lying westward of the eastern botindary of the 
district are those along the western base of the Eamagiri and the eastern base 
of the Nagari mountains, and some spreads in the valley of the Swarnamukhi 
river near the Madras railway at Karkambadi. In the two first of these areas 
the rock is much less coarsely conglomeratic than around the Alikur and Satta- 
vedu hills and over the Pyanur area. 
The surface of the Pyanur laterite patch is very thickly strewn with the ex¬ 
tremely coarse quartzite shingle weathered out of the underlying conglomerate, 
and in many places progress even on foot is by no means easy across the great 
smooth and highly slippery stones. The surface is so extremely stony that great 
tracts remain waste. That a very flat coicntry should be so inaccessible owing to 
the thickly strewn products of partial weathering of the rocks forming the surface 
is a very singular phenomenon. 
Remains of lateritic beds are very numerous to the westward of the present 
westerly boundaries of the formation, hlany such re- 
Debris of lateritic beds. noted as much as six or eight miles away from 
the nearest of tho undisturbed beds, and a closer search of the country would 
probably show such ruins even far further in that direction. The greater west¬ 
ward extension of the lateritic rocks, before adverted to, is thus abundantly 
proved. ^ 
Proofs that tho lateritic formations were, in part at least, formed since man s 
^ t advent on earth are numerously met with in the North 
implements. Arcot laterite patches in the form of well-shaped chipped 
implements of palseolithic types made of quartzite. Many of these were dis¬ 
covered by the geological surveyors in nearly all the lateritic patches, and in 
many cases also among the debris marking the sites of the now denuded parts 
of tho old extensions., e. g., among the gravelly ferruginous debris lying in the 
sui-face of the gneiss at and around the Arkonam railway junction at an eleva¬ 
tion of more than 300 feet above sea level. 
The highest elevations to which the implement-bearing lateritic rocks have 
f loi.AUi. been traced in this region are the neighbourhood of the 
l,eds. Madi’as railway at Karkambadi, in the Swarnamukhi 
valley, and the westernmost slopes of the Naikenpalem hills ; in the former case, 
the implements occur at an elevation of 370 feet above sea level, m the latter, 
at a probable elevation of between 600 and 600 feet. The Karkambadi beds 
yielded a great number of fine implements to the search of Mr. W. R. Robin- 
