Bme?vs — Petroleum and Oilfields. 123 



other. They may Tbe different portions of one and the same phe- 

 nomenon, but are there no differences between the chemical reactions 

 which at first, by a special mineralization, convert vegetable matter 

 into solid bitumen, in situ, and which are also assumed to convert 

 this same bitumen into a fluid again at the normal temperature, 

 to cool once more to the solid form ? It appears to us that, as far 

 as any proof is contained in Mr. Wall's paper, the source of the 

 fluid pitch may not lie at all in the stratified vegetable seams seen 

 near the surface, but in some far more deeply seated deposits, and 

 that the writer may have been misled by a similarity of appearance 

 and a contiguity in position to assume identity of origin. "We 

 advance the doubt cautiously, and in the hope of obtaining more 

 certain knowledge on the point. Mr. Wall's evidence, when made 

 clear, must be regarded as of more than ordinary importance, as it 

 seems to be the best stone in a structure that otherwise appears to 

 stand upon a ricketty basis. The theory, as applied to the sources 

 of Petroleum in North America, appears to have resulted from 

 difficulties in making all the circumstances of the case agree with 

 another and far more simple hypothesis. A " special mineraliza- 

 tion," or " fermentation " theory, to include both animal and 

 vegetable substances, according to need, in its operations, was 

 therefore built up to replace a " distillation " theory, which, though 

 well based, seemed at first sight incapable of explaining enough. It 

 has long ago been suggested that free bituminous products, more 

 especially those which rise to the surface as oils, are the results of a 

 natural distillation of bitumen-containing substances, such as lig- 

 nites and coals, by the action of the heat of the interior of the earth. 

 Now, considering that bituminous products can be obtained artifi- 

 cially from such substances by heat, and that Coal-beds, after their 

 formation, must, in very many instances, have been buried beneath 

 enormous accumulations of later date, and consequently have been 

 exposed to a great increase of temperature, there is o. prima facie case 

 in favour of this view. In anthracites we have further witnesses in 

 support of it, for these are coals which, having been exposed to the 

 supposed conditions, have parted with their contained hydro-carbons. 

 Such being our case, let us cross-examine the witnesses against it. 

 It has been said that the products of a natm-al and of an artificial 

 distillation of coal should be identical, which they are not ; but this 

 objection is of no value, since man and nature work under such 

 dissimilar conditions, that the utmost we can expect is a similarity, 

 far from an identity, of results. Geological proof , is given that 

 Petroleum occurs in localities far distant from any yielding coal, — in 

 rocks far older than any known to contain it, — and that the strata 

 in which it has been found have, to all appearance, never been 

 heated. The last is evidence actually in favour of the distillation 

 theory ; for the Hydro-Carbons having been driven ofi" from beds at 

 a high temperature, must have been condensed in strata which 

 remained cool, and if such strata were subsequently heated, they 

 would have to give off again the bituminous products which they 

 had temporarily retained. But, say the objectors, the Petroleum 



