720 THE MOLECULAR STRUCTURE OF MATTER. 



The process of the formation of petroleum seems to be the foUowiug: 

 It is generally admitted that the crust of the earth is very thin iu com- 

 l)arison with the diameter of the latter, and that this crust incloses soft 

 or fluid substance, among which the carbides of iron and of other metals 

 find a place. When, in consequence of cooling- or some other cause, a 

 fissure takes place through which a mountain range is protruded, the 

 crust of the earth is bent, and at the foot of the hills fissures are formed ; 

 or at any rate the continuity of the rocky layers is disturbed, and they 

 are rendered more or less porous, so that surface waters are able to make 

 their way deep into the bowels of the earth, and to reach occasionally 

 the heated deposits of metallic carbides, which may exist either in a 

 separated condition or blended with other matter. Under such circum- 

 stances it is easy to see what must take place. Iron, or whatever other 

 metal may be present, forms an oxide with the oxygen of the water ; 

 hydrogen is either set free or combined with the carbon which was as- 

 sociated with the metal, and becomes a volatile substance — that is, 

 naphtha. The water which had penetrated down to the incandescent 

 mass was changed into steam, a portion of which found its way through 

 the porous substances with which the fissures were filled, and carried 

 with it the vapors of the newly-formed hydro-carbons, and this mixture 

 of vapors was condensed wholly or in part as soon as it reached the 

 cooler strata. The chemical composition of the hydro-carbons produced 

 will depend upon the conditions of temperature and pressure under 

 which they are formed. It is obvious that these may vary between very 

 wide limits, and hence it is that mineral oils, mineral pitch, ozokerit, 

 and similar products differ so greatly from each other in the relative 

 proportions of hydrogen and carbon. I may mention that artificial pe- 

 troleum has been frequently prepared by a process analogous to that 

 descrilied above. 



It is needless to remark that Dr. Mendeleef's views are not shared by 

 every competent autiiority ; nevertheless, the remarkable permanence 

 of oil-wells, the apparently inexhaustibleevolution of hydro-carbon gases 

 in certain regions, almost forces one to believe that the hydro-carbon 

 products must be forming as fast as they are consumed, that there is 

 little danger of tbe demand ever exceeding the supply, and that there 

 is every prospect of oil being found in almost every portion of the sur- 

 face of the earth, es[)ecially in the vicinity of great geological disturb- 

 ances. Improved methods of boring wells will enable greater depths 

 to be reached ; and it should be remembered that, apart from the cost 

 of sinking a deep well, there is no extra expense in working at great 

 depths, because the oil generally rises to the snrface or near it. The ex- 

 traordinary pressures, amounting to 300 pounds per square inch, which 

 have been measured in some wells, seem to me to yield conclusive evi- 

 dence of the impermeability of the strata from under which the oil has 

 been forced up, and tend to confirm the view that it must have been 

 formed in regions far below any which could have contained organic 

 remains. 



