1898.] TECKIIAM — THE GENESIS OF BITUMENS. 137 



easily explained. The earliest forms of animal and vegetable life 

 are admitted to have been nearly destitute of nitrogen; hence when 

 these forms accumulated in sediments, which, borne down by depos- 

 its above them, invaded an isothermal that admitted of their distil- 

 lation, they must have been distilled, in the presence of steam, at 

 the lowest possible temperature ; they must have been distilled 

 under a gradually increasing pressure, the extent of which depended 

 upon the porosity of the sediments above them, up to the surface. 

 They must also have been distilled under a gradually increasing 

 temperature which would have been largely controlled by the pres- 

 sure. While the temperature and the pressure would have in every 

 instance been the least possible, with steam always present, these 

 physical conditions would on account of the varying porosity and 

 consequent varying resistance of the overlying mass have produced 

 very great effects in some instances and very slight effects in others. 

 As a consequence, we have in natural bitumens, as in artificial dis- 

 tillates, materials varying in density from natural gas to solid 

 asphaltum. 



If these distillates proceeded from materials that would yield 

 parafifine, these permanent and stable compounds, from marsh gas 

 to solid parafifine, remained in the receptacles that nature had pro- 

 vided for them until they were released by the drill. If, however, 

 the distillates proceeded from sediments of a different geological 

 age, containing animal and vegetable remains more highly organ- 

 ized, that would yield different series of hydrocarbons, with com- 

 pounds of nitrogen, then a very different bitumen would be stored 

 in these receptacles. Secondary reactions would convert these pri- 

 mary distillates into a great variety of substances. The contents 

 of the original reservoirs, borne down and invaded by heat, might 

 become involved in a second distillation at an increased pressure 

 and temperature. Fractures of these reservoirs from excessive pres- 

 sure might lead their contents to the surface along lines of contact 

 of strata or with water containing sulphates by which an originally 

 pure hydrocarbon would be converted into a sulphur bitumen. A 

 nitro hydrocarbon, reaching the surface under these conditions^ 

 might, by the combined action of evaporation and reaction with 

 sulphates, pass through all the varying degrees of density from pet- 

 roleum to maltha and become finally solid asphaltum, and this 

 through the lapse of time and abundance of material on a scale of 

 vast magnitude. 



