I. All writers have noticed the presence of limestone close to
petroleum fields in the United States and Canada, in the Caucasus, in
Burma, etc., but they have been most impressed by its being
"fossiliferous," or shell limestone, and have drawn the erroneous
inference that the animal matter once contained in those shells
originated petroleum; but no fish oil ever contained paraffin. On the
other hand, the fossil shells are carbonate of lime, and, as such,
capable of producing petroleum under conditions such as many limestone
beds have been subjected to in all ages of the earth's history. All
limestone rocks were formed under water, and are mainly composed of
calcareous shells, corals, encrinites, and foraminfera--the latter
similar to the foraminfera of "Atlantic ooze" and of English chalk
beds. Everywhere, under the microscope, the original connection of
limestone with organic matter--its organic parentage, so to speak, and
cousinship with the animal and vegetable kingdoms--is conspicuous.
When pure it contains 12 per cent. of carbon.
Now petroleum consists largely of carbon, its average composition
being 85 per cent. of carbon and 15 per cent. of hydrogen, and in the
limestone rocks of the United Kingdom alone there is a far larger
accumulation of carbon than in all the coal measures the world
contains. A range of limestone rock 100 miles in length by 10 miles in
width, and 1,000 yards in depth, would contain 743,000 million tons of
carbon, or sufficient to provide carbon for 875,000 million tons of
petroleum. Deposits of oil-bearing shale have also limestone close at
hand; e.g., coral rag underlies Kimmeridge clay, as it also underlies
the famous black shale in Kentucky, which is extraordinarily rich in
oil.
II. As evidence of volcanic action in close proximity to petroleum
strata, the mud volcanoes at Baku and in Burma are described, and a
sulphur mine in Spain is mentioned (with which the writer is well
acquainted), situated near an extinct volcano, where a perpetual gas
flame in a neighboring chapel and other symptoms indicate that
petroleum is not far off. While engaged in studying the geological
conditions of this mine, the author observed that Dr. Christoff
Bischoff records in his writings that he had produced sulphur in his
own laboratory by passing hot volcanic gases through chalk, which,
when expressed in a chemical formula, leads at once to the postulate
that, in addition to sulphur, _ethylene_, and all its homologues
(C_{n}H_{2n}), which are the oils predominating at Baku, would be
produced by treating:
2, 3, 4, 5 equivs. of carbonate of lime (limestone) with
2, 3, 4, 5 " sulphurous acid (SO_{2}) and
4, 6, 8, 10 " sulphureted hydrogen (H_{2}S);
and that marsh gas and its homologues, which are the oils
predominating in Pennsylvania, would be produced by treating:
1, 2, 3, 4, 5 equivs. of carbonate of lime with
1, 2, 3, 4, 5 " sulphurous acid and
3, 5, 7, 9, 11 " sulphureted hydrogen.
Thus we find that:
Carbonate of lime, 2CaCO_{3}, } { 2(CaSO.H_{2}O) (gypsum),
Sulphurous acid, 2SO_{2}, and } yield { 4S (sulphur), and
Sulphureted hydrogen, 4H_{2}S, } { C_{2}H_{4}, which is
{ _ethylene_.
And that:
Carbonate of lime, CaCO_{3} } { (CaSO_{4}.H_{2}O) (gypsum),
Sulphurous acid, SO_{2}, and } yield { 3S (sulphur) and
Sulphureted hydrogen, 3H_{2}S, } { CH4, which is marsh gas.
So that these and all their homologues, in fact petroleum in all its
varieties, would be produced in nature by the action of volcanic gases
on limestone.
But much the most abundant of the volcanic gases appear at the surface
as steam, and petroleum seems to have been more usually produced
without sulphurous acid, and with part of the sulphureted hydrogen
(H_{2}S) replaced by H_{2}O (steam) or H_{2}O_{2} (peroxide of
hydrogen), which is the product that results from the combination of
sulphureted hydrogen and sulphurous acid:
(H_{2}S + SO_{2} == H_{2}O_{2} + 2S).
It is a powerful oxidizing agent, and it converts sulphurous into
sulphuric acid. Thus:
CaCO_{3} } { CaSO_{4}.H_{2}O (gypsum)
H_{2}S, } yield { and
2H_{2}O, } { CH_{4}, which is marsh gas.