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