YENANGYOUNG. 63 



c. The occurrence of petroleum. — At Yenangyoung the upper 

 miocene beds are of great economical importance, because of the 

 petroliferous beds they contain, which have yielded, comparatively 

 speaking, a large quantity of petroleum. 



It has been proved to a certainty that in the Yenangyoung oil 

 field the petroleum is always associated with the arenaceous beds, 

 that is to say, the sandstone is always saturated with petroleum, 

 while in no case is it present in the argillaceous beds, or, as might 

 perhaps be expected, gathering in their fissures or cracks. The clay 

 beds seem to act like a hermetic seal, as is well illustrated in all 

 cases where native wells have just reached the upper part of the 

 petroliferous sands. It seems that towards the top thin beds of 

 clay alternate with the sand, which finally passes into clay. The 

 sand is always charged with oil, and exhibited its fine green colour, 

 while the clay contains no trace of it. I also frequently observed 

 that when breaking a fair sized lump of clay and, as is often the 

 case, it contained a lenticular thin layer of sand, this sand was 

 often full of oil, although no trace of it could be seen superficially. 

 I want to put stress on the fact that I did not observe this once, 

 but repeatedly, and that I was very particular in verifying the 

 correctness of this observation, which seemed to me of the greatest 

 theoretical importance, inasmuch as it sheds a light on the origin 

 of the oil. I may remark here that this mode of occurrence 

 renders it impossible, that the petroleum should have originated 

 at some other place and migrated to its present receptacle. It is 

 impossible to imagine how it could have penetrated a fairly thick 

 layer of clay without leaving the slightest traces of the way is 

 followed, and eventually gathered in a sandy streak. If this view is 

 taken, the question might well be raised why, if such a force existed, 

 was not the petroleum again driven out from the sandy layer. To 

 me this proof seems convincing that either the substances eventu- 

 ally changed into petroleum, or the petroleum itself must have 



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