318 
POPULAR SCIENCE REVIEW. 
to be attributed to the tendency which it possesses to traverse higher and* 
porous sedimentary deposits when exposed to the action of water universally 
present, and of greater density than itself. The beds of sandstone in which 
much of the oil is met with do not appear to contain the remains of the- 
organisms to which its origin is ascribed, and the geologist is driven to seek 
at greater depths the materials which yield it. In the Caucasus the oil 
occurs in Tertiary beds ; in Pennsylvania, in Devonian and Silurian rocks.. 
But, the author maintains, we have no grounds for believing in the occur- 
rence of any extensive deposits of organized structures at a period earlier 
than the Silurian, and the prevailing view, therefore, can hardly be considered 
to meet the difficulty. Mendelejeff refers to the theories put forth by 
Laplace and others respecting the probable mode of formation of our globe,, 
its density as compared with that of the surface layers, so far as we are 
acquainted with them, &c., and draws attention to the possibility of the 
interior of the earth containing metallic masses of vast extent. If it be 
allowed that iron is the prevailing metal — and its presence in great quan- 
tities in the sun and in meteorites renders his theory a not improbable one 
— and that metal occurs in combination with carbon, we have the material 
from which we can conceive the mineral oil to have been derived. Contact 
with water at high temperatures, and under great pressure, brought about 
by the upheaval or disruption of any of the overlying sedimentary strata,, 
would result in the formation of metallic oxides and saturated hydrocarbons. 
The latter, permeating the porous sandstones of higher levels, would con- 
dense there, or, after undergoing further change, become the marsh gas of 
the “ gas-wells,” or be converted into unsaturated hydrocarbons. The- 
invariable association of salt water with mineral oil is not without its bearing 
on this interesting question. If the view recently advanced by Steenstrup, 
that the remarkable metallic masses, discovered by Nordenskj old, in 1870, at 
Ovifak, Disko Island, Greenland, and generally held to be blocks of meteoric 
iron, be a correct one, and they are really erupted matter and not ofcosmical 
origin, they narrowly resemble, as regards their composition, which analysis 
has shown to be to a considerable extent carbide of iron and magnetite, the- 
material which Mendelejeff assumes to be the source of the oil. 
Ihleite . — Schrauf has given this name to a ferric sulphate which he has 
found on the graphite of Mugrau, in Bohemia. It is a product of the 
decomposition and oxidation of the pyrites disseminated through the grapnite, 
and occurs as a fine orange-yellow efflorescence upon its surface ; it exhibits 
the botryoidal characters of botryogen. It has a density of 1*812, and is 
soluble in cold water. Specimens which were collected in 1875 and the* 
following year were found to have the following composition : — 
1875. 
1876. 
Sulphuric acid 
38*2 
37*4 
37*2 
Iron protoxide . 
2*1 
j- 26*1 
1*4 
Iron peroxide . 
' j- 24*5 
J 25*6 
Alumina 
0*3 
Lime 
0*4 
0-3 
Water . 
35 *5 
35*6 
35.3 
100*3 
99’8 
99*8 
