R. Zaloziecki, in _Dingl. Polyt. Jour._, gives a lengthy physical and
chemical argument in favor of the modern view that petroleum and
paraffin owe their origin to animal sources; that they are formed from
animal remains in a manner strictly analogous to that of the formation
of ordinary coal from wood and other vegetable debris. For geological
as well as chemical reasons, the author holds that Mendeleeff's theory
of their igneous origin is untenable, pointing out that the
hydrocarbons could not have been formed by the action of water
percolating through clefts in the gradually solidifying crust until it
reached the molten metallic carbides, as these clefts could only occur
where complete solidification had taken place, and between this point
and the metallic stratum a considerable space would be taken up by
semi-solid, slag-like material which would be quite impervious to
water. Under the conditions, too, existing beneath the surface of the
earth, such polymerization as is necessary to account for the presence
of the different classes of hydrocarbons found in petroleum is
scarcely credible.
On the other hand it is to be specially noticed that, with a few
unimportant exceptions, all bituminous deposits are found in the
sedimentary rocks, and that just as these are constantly changing in
composition, so the organic matter present changes, there being a
definite relationship between the chemical constitution of the
petroleum and the age of the strata in which it is found. It is almost
certain that in the most recent alluvial formations no oil is ever
found, its latest appearance being in the rocks of the tertiary
period, the place where the solid paraffin is almost exclusively met
with; thus helping to show that the latter has been formed from the
decomposition of the oil, and is not a residue remaining after the oil
has been distilled off. To this conclusion the fact also strongly
points, that the paraffin is much simpler in constitution, purer, and
often of far lighter color than the crude oil, which could not be the
case if it were the original substance.
On examining by the aid of a map the position of the chief oil-bearing
localities it will be noticed that the most prolific spots follow
fairly accurately the contour lines of the country, so that at one
time they formed in all probability a coast line whereon would be
concentrated for climatic reasons most of the animal life both of the
land and sea. During succeeding generations their dead bodies would
accumulate in enormous quantities and be buried in the slowly
depositing sand and mud, till, owing to the gradual alterations of
level, the sea no longer reached the same point. This theory is borne
out by the fact that oil deposits are usually found in marine
sediments, sea fossils being frequently met with. The first process of
the decomposition of the animal remains would consist in the formation
of ammonia and nitrogenous bases, the action being aided by the
presence of air, moisture, and micro-organisms, at the same time,
owing to the well known antiseptic properties of salt, the
decomposition would go on slowly, allowing time for more sand and
inorganic matter to be deposited. In this way the decomposing matter
would be gradually protected from the action of the air, and finally
the various fatty substances would be found mixed with large amounts
of salt, under considerable pressure, and at a somewhat high
temperature. From this adipocere, fatty acids would be gradually
formed, the glycerol being washed away, and finally the acids would be
decomposed by the pressure into hydrocarbons and free carbonic acid
gas. That many of these hydrocarbons would be solid at ordinary
temperatures, forming the so-called mineral wax, which exists in many
places in large quantities, is much easier to imagine, in the light of
modern chemical knowledge, than that the fatty acids were at once
split up into the simpler liquid hydrocarbons, to be afterward
condensed into the more complex molecular forms of the solid
substance.
In this way from animal matter are in all probability formed the vast
petroleum deposits, the three substances, adipocere, ozokerite, and
petroleum oil being produced in chronological order, just as lignite,
brown coal and coal are formed by the gradual decomposition of
vegetable remains.
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