{ C_{2}H_{4}, which is _ethylene._

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

_Formulae Showing how Ethylene and its Homologues
(C_{n}H_{2}{n}) are Produced by the Action of the Volcanic
Gases H_{2}S and H_{2}O_{2} on Limestone._

Carbonate Sulphureted Peroxide of Ethylene and
of lime. hydrogen. hydrogen. Gypsum. its homologues.

2CaCO3 + 2H2S + 2H2O2 yield 2(CaSO4.H2O) + C2H4 ethylene
(gaseous).
3CaCO3 + 3H2S + 3H2O2 " 3(CaSO4.H2O) + C3H6
4CaCO3 + 4H2S + 4H2O2 " 4(CaSO4.H2O) + C4H8
5CaCO3 + 5H2S + 5H2O2 " 5(CaSO4.H2O) + C5H10
6CaCO3 + 6H2S + 6H2O2 " 6(CaSO4.H2O) + C6H12
Boiling
point.
7CaCO3 + 7H2S + 7H2O2 " 7(CaSO4.H2O) + C7H14 --
8CaCO3 + 8H2S + 8H2O2 " 8(CaSO4.H2O) + C8H16 189 deg.C.
9CaCO3 + 9H2S + 9H2O2 " 9(CaSO4.H2O) + C9H18 136 deg.C.
10CaCO3 + 10H2S + 10H2O2 " 10(CaSO4.H2O) + C10H20 160 deg.C.
11CaCO3 + 11H2S + 11H2O2 " 11(CaSO4.H2O) + C11H22 180 deg.C.
12CaCO3 + 12H2S + 12H2O2 " 12(CaSO4.H2O) + C12H24 196 deg.C.
13CaCO3 + 13H2S + 13H2O2 " 13(CaSO4.H2O) + C13H26 240 deg.C.
14CaCO3 + 14H2S + 14H2O2 " 14(CaSO4.H2O) + C14H28 247 deg.C.
15CaCO3 + 15H2S + 15H2O2 " 15(CaSO4.H2O) + C15H30 --

It is explained that these effects must have occurred, not at periods
of acute volcanic eruptions, but in conditions which maybe, and have
been, observed at the present time, wherever there are active
solfataras or mud volcanoes at work. Descriptions of the action of
solfataras by the late Sir Richard Burton and by a British consul in
Iceland are quoted, and also a paragraph from Lyall's "Principles of
Geology," in which he remarks of the mud volcanoes at Girgenti
(Sicily) that _carbureted hydrogen_ is discharged from them, sometimes
with great violence, and that they are known to have been casting out
water, mixed with mud and _bitumen_, with the same activity as now for
the last fifteen centuries. Probably at all these solfataras, if the
gases traverse limestone, fresh deposits of oil-bearing strata are
accumulat