TRANSACTIONS OF SECTION G. 727 



regards the stowage of a cargo so eminently shifting, and with respect to risk 

 from tire and from explosion. 



The enonuous consumption of petroleum and of natural gases frequently raises 

 the question as to the probability of the proximate exhaustion of the supply ; and, 

 without doubt, many fear to adopt the use of oil, from a feeling that if such use 

 once becomes general the demand will exceed the jjrodtiction, the price will rise 

 indetinitely, and old methods of illumination, and old forms of fuel, will have to 

 be reverted to. From this point of view it is most interesting to inquire what are 

 the probabilities of a continuous supply ; and such an investigation leads at once to 

 the question, ' What is the origin of petioleum ? ' In the year 1877 Professor 

 Mendeli^eir undertook to answer this question ; and as his theory appears to be very 

 little known, and has never been fully set fortii in the English language, I trust 

 you will forgive me for laying a matter so interesting before you. Dr. Mendeleeff 

 commences his essay by the statement that most persons assume, without any 

 special reason — excepting, perhaps, its cliemical composition — that naphtha, like 

 coal, has a vegetable origin. He combats this hypothesis, and points out, in the first 

 place, that naphtha must have been formed in the dejiths of the earth. It could 

 not have been produced on the surface, because it would have evaporated ; nor over 

 a sea bottom, because it would have floated up and been dissipated by the same 

 means. In the next place he shows that naphtha must have been formed beneath 

 the very site on which it is found — tliat it cannot have come from a distance, like so 

 many other geological deposits, and for the reasons given above, namely, that it 

 could not be water-borne, and could not have flowed along the surface, while in 

 the superficial sands in which it is generally found no one has ever discovered the 

 presence of organised matter in sufiiciently large masses to have served as a source 

 for the enormous (juantity of oil and gas yielded in some districts; and hence it ia 

 most probable that it has ris(-n from much greater depths under the influence of 

 its own gaseous pressure, or fioated up upon the surface of water, with which it is 

 so frequently associated. 



The oil-bearing strata in Europe belong chiefly to the Tertiary or later geologi- 

 cal epochs ; so that it is conceivable that in these strata, or in those immediately 

 below them, carboniferous deposits may exist and may be the sources of the oil ; 

 but in America and in Canada the oil-bearing sands are found in the Devonian 

 and Silurian formations, which are either destitute of organic remains, or contain 

 them in insignificant quantities. Yet if the immense masses of hydrocarbons have 

 been produced by chemical changes in carboniferous beds, equally large masses of 

 solid carboniferous remains must still exist ; but of this there is absolutely no 

 evidence, while cases occur in Pennsylvania where oil is obtained from the 

 Devonian rocks underlying compact clay beds, on which rest coal-bearing strata. 

 Had the oil been derived from the coal, it certainly would not have made its way 

 downwards ; much less would it have penetrated an impermeable stratum of clay. 

 The conclusion arrived at is, that it is impossible to ascribe the formation of nai'htha 

 to chemical changes produced by heat and pressure in ancient organised remiuns. 



One of the first indices to the solution of the question lies in the situation of 

 the oil-ljearing regions. They always occur in the neighbourhood of, and run 

 parallel to, mountain ranges, — as, for example, in Pennsylvania, along the Alle- 

 ghanies ; in Russia, along the Caucasus. The crests of the ranges, formed originally 

 of horizontal strata which had been forced up by internal pressure, must have been 

 cracke<l and dislocated, the fissures widening outwards, while similar cracks must 

 have been formed at the bases of the ranges ; but the fissures would widen down- 

 wards, and would form channels and cavities into which naphtha, formed in the 

 depths to which the fissures descended, would rise and manifest itself, especinlly in 

 localities where the surface had been sufficiently lowered by denudation or other- 

 wise. 



It is in the lowest depths of these fissures that we must seek the laboratories in 

 which the oil is formed ; and once produced, it must inevitably rise to the surface, 

 whether forced up by its own pent-up ga.--es or vapours, or floated up by associated 

 water. In some instances the oil penetrating or soaking tiirou!.'h the surface 

 layers loses its more volatile constituents by evaporation, and, in consequence, 



