70 
Records of the Geological Survey of India. 
[voi. Vf, 
It may here be remarked that whereas the only known petroleum localities lie within 
the area of unaltered nummulitic strata, or of the newer Tertiaries, yet the greater number 
of salt springs lie below this horizon among the altered and presumedly lower members of 
the same group; a point which, if definitely established, as it seems to be, as far as regards 
the area hitherto subjected to examination, will not be without an important practical 
bearing in searching for petroleum, inasmuch as there is an idea prevalent that the presence 
of brine springs in this region is per se indicative of the existence below of the more 
valuable mineral. Having regard to the circumstances under which the mineral oils occur 
in America, there is nothing unreasonable in the supposition of a similar connexion existing 
between the brine springs and oil in Pegu, as is found in the new world—an idea strengthened, 
moreover, by the existence in the same districts of both oil and brine; but, as I have already 
pointed out, there seems no good reason for believing that, in Pegu, the same connexion be¬ 
tween brine springs and oil exists as in the American oil-fields. On the contrary, it would 
seem that the reverse of what occurs in America is to be anticipated here. In America 
the connexion between the oil and brine is an established fact; the first petroleum obtained 
by boring having been accidentally obtained in 1819 “in sinking wells for salt in the little 
Maskingum river in Ohio,” (Erni, “ Coal-oil and Petroleum.”) In Pegu, it would seem as 
though, if in sinking a bore, a copious brine spring were struck, this would probably indicate 
that the boring had penetrated to a horizon below that wherein the mineral oil was pro¬ 
duced. In Pegu, as in America, the oil may rise to the surface with the brine, as the 
horizon of the naptbagenie beds is higher than the sources of the brine, which is not the 
case in the American oil-field. But the non-association of the two in Pegu may, I think, 
be legitimately inferred from the fact of no indications of petroleum being known within 
the belt of rocks wherein the most numerous brine springs rise, as would hardly tail to be the 
case were the origin of the brine and petroleum in one and the same group of beds. That the 
co-existence, too, of brine springs and petroleum in Pegu is rather a fortuitous than a connected 
phenomenon (as it would seem to be in America,) is to some extent borne out by' the fact 
of petroleum occurring in the Punjab in connexion with rocks of the same geological ago 
as in Pegu, but without the accompaniment of brine springs, as in that province; so that 
our present experience may be summed up with the assertion, that whilst a copious discharge 
of brine and marsh-gas may not be without value in determining a site for sinking for 
petroleum, in ground occupied by rocks of the upper portion of the nummulitic group or any 
rocks above that horizon, yet the same indications are not to be relied on as of equal 
promise, within the area occupied by rocks lower in the series, or of greater geological age. 
It only remains to add a few words explanatory of my classing these altered or hill 
rocks as ‘ Negrais beds,’ or possibly nummulitic in part, after having, in my recent paper on 
the ‘ Axials in Western Prorne,’ included them in that group. When writing that paper, 
the age of these hill-rocks was q uite problematical, and beyond the general absence of 
fossils in the limestones and the mineral character of the beds, so different from that oi the 
recognised Nummulitics, there was little or no evidence to which group they should be 
assigned; and the balance seemed to tend towards their union with the older or axial group. 
During the following season, however, (1870-71), I accumulated evidence, ol an opposite 
tendency, not only by a more extended examination of the ground occupied by them, but I 
had the good fortune likewise to detect Nummulites in one ol the outcrops of limestone, alluded 
to by me in note at page 38 (loc. cit.), which I had not previously had the opportunity ot 
visiting, thereby demonstrating the relation of a portion at least of these bill rocks, of 
hitherto uncertain age, with the newer nummulitic group, in spite of their often excessively 
changed character, rather than with the older Axials, with which they had been previously in¬ 
cluded. I must defer, however, a discussion of this question for another occasion. 
Calcutta, ) W. THEOBALD. 
6 tli August 1872. / 
