444 
SILURIA. 
[Chap. XVIII. 
worthy of remark that in Gaspe", in the eastern subdivision of the great Palaeozoic 
basin, where the whole of the Devonian consists of sandstones, the pure lime- 
stones which there represent the Upper Silurian are oleiferous. 
The observations of Professors Andrews and Evans of Ohio, as well as those of 
Dr. Sterry Hunt, have shown that the available supplies of oil are met with along 
the crowns of gentle undulations, where fissures, often nearly vertical, contain 
the accumulation of ages, frequently accompanied by quantities of gas, whose 
elasticity raises the oil to the surface and gives rise to the flowing or spouting 
wells. A certain amount of undulation is thus required to facilitate the accu- 
mulation of the oil (which from its levity ascends to the higher parts of the strata), 
and also to give rise to the requisite fissures or reservoirs. Too great a dis- 
turbance of the rocks, however, allows the oil to run to waste. Its alteration 
by evaporation and by oxidation in fissures gives rise to solid matters, which 
vary from a kind of asphalt to more or less insoluble coal-like bodies like what 
have been named Albertite and Grahamite. These matters fill great veins in 
the Carboniferous rocks of West Virginia, and are also described by Dr. Hunt 
as occurring in Lower Silurian rocks in Canada, where they are found lining or 
filling fissures, and sometimes assuming mammillary or stalactitic forms. Such 
materials are even met with in veins in the old Laurentian limestones, con- 
verted, however, into something like anthracite. According to Dr. S. Hunt, it 
is to the comparatively undisturbed character of the Palaeozoic rocks of North 
America that the preservation in them of such large quantities of petroleum is 
due ; and he supposes that this substance was once not less widely distributed 
in the Palaeozoic rocks of other regions, where, however, the conditions for its 
preservation have been less favourable than in North America *. In those parts 
of North America where the oleiferous strata are nearly or quite horizontal, the 
borings seem to have yielded little or no petroleum, for the obvious reason that 
the inclination of the strata which would enable the oil to ascend through the 
joints of the strata to higher levels is there wanting. This relation of the oil to 
the lines of uplift is remarkably seen, says Dr. Hunt, along the great Cincinnati 
anticlinal, a gentle undulation which stretches from the head of Lake Ontario 
in a south-western direction for about 500 miles to the Cumberland Valley in 
Kentucky, dividing the great carboniferous areas of North America. This anti- 
clinal brings up in the Cumberland region the Lower Silurian strata rich in 
petroleum, but near its north-eastern extremity is covered by the Middle and 
Lower Devonian strata, in which are sunk the oil-wells of Western Canada. 
The further relation of these to the numerous subordinate undulations, parallel 
to the great anticlinal, is shown in detail in the Eeport on the Geology of 
Canada for 1866. 
Petroleum is generally associated with saline waters, and, according to 
Dr. Hunt, for the very obvious reason that the comparatively undisturbed 
marine strata in which it occurs are everywhere permeated by the water of the 
primeval oceans, which naturally finds its way to the surface along the same 
lines as the petroleum. In addition to these ancient sea- waters, true saliferous 
formations exist in many regions, and yield pure brines from the solution of rock- 
salt. These formations, however, belong to different and distinct formations 
from those bearing petroleum. Thus, in Western Canada, after penetrating the 
Lower-Devonian oil-horizon, the gypsiferous and salt-bearing Onondaga formation 
of the Upper Silurian is encountered; and in the adjacent parts of the United 
* It is worthy of remark that the great supplies of petroleum in most other parts of the world are 
derived from Mesozoic and Csenozoic formations. 
