124 Reviews— Petroleum and Oilfields. 



reservoirs are frequently in rocks older, and therefore inferior, in 

 position to the lowest known Goal-measures, and if the latter had 

 been heated, the former must have been more so. This objection 

 assumes that the condensed substances are fovind now on the very 

 spot where they were originally distilled. But, suppose distilla- 

 tion to have taken place in the heated and upthrown Coal-measures 

 now forming the Appalachian Chain, the distilled products would 

 have found their way down the subterranean slopes of the colder 

 rocks, flanking the actual site of disturbance, until penetrating 

 cracks and fissures, they found a permanent resting-place upon an 

 impervious series of unheated rocks, far distant from, and quite 

 possibly below, in geological position, the Carboniferous strata from 

 which they had their origin. We may even imagine a case, where 

 the vapours and oil, retained for a time in higher rocks, may, when 

 a cooling of the beds below occurred, have drained downwards 

 through the very strata from which they had been expelled, into 

 reservoirs below ; or, again, products driven off from a disturbed 

 region, may have drained away to a position below an unaffected 

 series of Coal-measures. We must remember, too, in connection with 

 this subject, the probability, nay the certainty, that immense masses 

 of carbonized vegetation may have been denuded from localities 

 where we now find oil, but neither coal nor lignite. Many corrobo- 

 rative items of evidence in favour of, or at least not inconsistent with, 

 the distillation theory, will occur to the investigator of the subject ; as, 

 for instance, the nature of the ground in which the oil is found, the 

 very rifts and fissures into which the boring rods fall being the 

 ancient drains by which the Hydro-Carbons found their way from 

 the great natural stills to the permanent receivers. 



To sum up the evidence in favour of either of the two theories ; 

 the case to our mind stands thus,— That vegetable matter, in be- 

 coming bituminized, or converted into lignite and coal, undergoes 

 processes of mineralization varying according to the diverse condi- 

 tions in which such vegetable deposits may be placed, we admit ; but 

 further proof is required to show that djaj such special mineralization 

 will produce free bitumen. Still less are we inclined to admit, 

 without anything save conjectural hypothesis to support the view, 

 that the remains of animals may be so converted. On the other 

 side, it is a fact that Hydro-Carbons may be derived from pre- 

 existing bituminized substances ; and, so far from seeing physical 

 and Geological objections to this view, it appears to us that the 

 circumstances under which free bituminous substances are described 

 as occurring in Nature, are not merely not inconsistent with such an 

 origin, but actually, in some cases, such as we should a priori expect. 

 Let us be clearly understood. The chemical action which reduces 

 vegetable substances to a carbonized state may, possibly, under 

 favourable circumstances, be carried on to a second stage, and 

 liberate Hydro-Carbons from the resu.lts of the first. Possibly 

 the conditions may be such that the chemical action of the first 

 stage is so energetic as to develop in itself an amount of 

 heat sufficient for the accomplishment of the second. Mr. Wall's 



