152 
Records of the Geological Surveg of India. [voL. xii. 
concretions. Tlie sandy beds occupy the lower slopes near the delta or the band 
of marine alluvium bordering the coast, while the conglomeratic beds occupy 
the higher grounds to the west and often overlajj widely on to the gneiss. 
The various rivers which convey the drainage of the country to the sea 
Sub-divlsiou of lute- divide the lateritic region into a number of minor areas or 
iitic aiea. patches amounting in all to nine. Their sizes are very 
unequal as might be expected, ranging as they do from several hundred square 
miles to only a few dozen or so in extension. Taking them from north-east to 
south-west the first is the Tanpre igatch, so called from the fact of its being the 
southward continuation of the great patch, on the northern edge of which stands 
the famous old town of Tanjoro, five miles beyond the northern limit of the map. 
This is followed southward of the Ikani-ar by the Fudulcotai patch, which is 
divided by the Vellar from the Shenkarai patch. South of the Pamb-ar lies 
another patch of laterite which I will designate as the Skdlihotai (Shawcotta) 
•patch. South of the Manimut-Sr is a small patch which may conveniently be 
called the Sei-rwcayal patch. The most southerly spread of lateritic rocks to be 
described lies around Sivaganga and should be named accordingly the Sivaganga 
pjatch. Two of the remaining patches to be considered lie to the westward of the 
general run of the patches close to the town of Tripatur, after which they may be 
siTitably called the north a,ndi south Tripatur patches. The ninth and la,st patch 
lies at the westei’n extremity of the Tanjore patch on the border of the countiy 
included in sheet 79; it may for convenience be called the Nallur patch. A 
great number of little patches too minute to be mapped are dotted over the 
gneiss area at various distances from the present laterite boundaiy, showing that 
its former westward extension was considerably greater than it is at present, 
and that great 2 Jart of the original deposits has been removed by denudation. 
Some of the smaller of the far outlying patches have undergone so much change 
from weathering and reconsolidation that they might almost be reckoned as 
subaerial formations. 
The most remarkable spreads of conglomeratic laterite are to be seen along 
Tanjore patch western boundary of the areas in nearly every case, 
but only a few of them need be specially mentioned. To 
begin with the Tanjore patch. Vast sheets of laterite conglomerate are to bo 
seen to the west and south of Gandarakotai. A little to the north of Suriam- 
j)atti* esjiecially the bare black sheets of rock arranged in terraces with low steps 
give the country a strange ajjpearance. Where the conglomerate is covered with 
soil the latter is generally a very hard compact sandy clay of red or yellow (bath- 
brick) color much marked by sun-cracks, which run in very regular systems 
and give the soil a tesselated appearance on a largo scale. In the presence of 
v\ ater these lateritic soils are fertile, but the high dry downs they are oftenest 
seen ujion are generally waste, and bear but little else than a very low scrub of 
Dodonma viscosa mixed with a few dwarf Mimosa. 
This low Dodonaa scrub is quite a feature of the hard lateritic soil ti-acts, 
and many instances of it might bo adduced. The yellow soil especially assumes 
’ Pothaiiavial of Atlas map. 
