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 (H2S) replaced by H2O (steam) or H2O2 (peroxide of hydrogen), which is the product that results from the combination of sulphureted hydrogen and sulphurous acid:

(H2S + SO2 == H2O2 + 2S).

It is a powerful oxidizing agent, and it converts sulphurous into sulphuric acid. Thus:

CaCO3
H2S,
2H2O,		}yield{(CaSO4.H2O) (gypsum)
and
CH4, which is marsh gas.

And

2CaCO3
2H2S,
2H2O2,		}yield{2CaSO4.H2O
and
C2H4, which is ethylene.

Tables are given showing the formulæ for the homologues of ethylene and marsh gas resulting from the increase in regular gradation of the same constituents.

Formulæ Showing how Ethylene and its Homologues (CnH2n) are Produced by the Action of the Volcanic Gases H2S and H2O2 on Limestone.

Carbonate of lime.Sulphureted hydrogen.Peroxide of hydrogen.Gypsum.Ethylene and its homologues.
2CaCO3+2H2S+2H2O2yield2(CaSO4.H2O)+C2H4ethylene (gaseous).
3CaCO3+3H2S+3H2O2"3(CaSO4.H2O)+C3H6
4CaCO3+4H2S+4H2O2"4(CaSO4.H2O)+C4H8
5CaCO3+5H2S+5H2O2"5(CaSO4.H2O)+C5H10Boiling
6CaCO3+6H2S+6H2O2"6(CaSO4.H2O)+C6H12point.
7CaCO3+7H2S+7H2O2"7(CaSO4.H2O)+C7H14—
8CaCO3+8H2S+8H2O2"8(CaSO4.H2O)+C8H16189°C.
9CaCO3+9H2S+9H2O2"9(CaSO4.H2O)+C9H18136°C.
10CaCO3+10H2S+10H2O2"10(CaSO4.H2O)+C10H20160°C.
11CaCO3+11H2S+11H2O2"11(CaSO4.H2O)+C11H22180°C.
12CaCO3+12H2S+12H2O2"12(CaSO4.H2O)+C12H24196°C.
13CaCO3+13H2S+13H2O2"13(CaSO4.H2O)+C13H26240°C.
14CaCO3+14H2S+14H2O2"14(CaSO4.H2O)+C14H28247°C.
15CaCO3+15H2S+15H2O2"15(CaSO4.H2O)+C15H30—