136 
Recorih of Ihe Geological Stirveg of hulia. 
[voL. XIIT. 
The stratigraphy of the formations oklei' than the alluvium is thus so far 
favorable for artesian borings, were the latter carried to a sufficient depth; but it 
is just this depth and the probability of having to pass through the hard and 
coarse grits and conglomerates of the Cnddalore sandstones which would make 
them impracticable. 
Considerations on other localities suitable for artesian wells. 
The wells are then sunk in the northerly seaward corner of an extensive coastal 
alluvial plain or basin, into which flow two larg’e rivers whose waters may be 
relied on in great measure for keeping the permeable strata well tilled, and which 
spreads back far enough from the coast for its surface inclination to give a 
head to these waters. Such is the broad and patent condition of affairs here; 
hence in enquiring as to the suitability of other parts of the Coromandel (or 
even further inland) for artesian borings, the most evident requirement i.s 
that they should have all the capabilities of the Pondicherry-Cnddalore basin 
to ensnre success. 
Nevertheless, there are certain points (some of them already hinted at) 
Doubts as to tlie ne- which make me doubt whether the size of this basin 
ccssity for so large a or the large supply of water received into it, or even 
the head attainable at the entrance of the rivers on the 
plain, are really necessary for the discharge and hydrostatic level attained. It is 
a question with me whether, for instance, the same hydrostatic level could not 
be attained W’itli a much lower head, at a lesser distance from the vents ; there 
being no doubt that the supply of water, obtained so far, is not beyond what 
the Ariancup river could give to ah.sorbent strata only a few miles from its 
month. The irregular oscillations of the water rise in the southern bore holes ; 
and the failure of a rise in the Ville Noire boring through all the strata which 
appear to correspond to those of the fonner wells and for such a depth seem 
also to point to a head not far distant, and only a moderate supply of water. 
I find it hard too to believe in the implied gi'eat extension of the impei'vious 
Beams or bands met within the borings ; the few outcrops of alluvial strata which 
I have seen in high river banks having generally given indications of ultimate 
thinning out within comparatively short distances, for the most part up, but 
very often down, the river’s course. It is again difficult for one to conceive 
that the borings, so very shallow in such a wide plain, south of the town, have 
run down anjnvhere near strata holding W’ater absorbed in the higher reaches 
of the riv'ers within the edge of the basin. 
The town of Cnddalore, situated as it is at the southern seaward corner of the 
same basin, is, on the face of it, the most obvious place 
to try first. Put the city of Madras is for many reasons 
the more important site. At the same time, there would 
appear to be even better sites than Cnddalore, on the deltas of the Cauvery, 
Pennffi’, Kistna, and Godavari. 
Madras, though on the edge of a remarkably long belt of coastal alluvium, 
Madras at first sight directly in front of only a small alluvial bay or plain, 
not so favorably situat- very much smaller than that of the Fi'ench settlement: 
so that if it were necessary to go entirely on the charac- 
Otber localities of al¬ 
luvial deposits. 
od. 
