YENANGYOUNG. 



67 



wells are most probably only parts of one and the same layer, 

 separated by local argillaceous beds. It seems, however, certain 

 that below the fourth oil sand there is a fifth layer containing petro- 

 leum, which most probably reaches a great thickness. It has been 

 observed in wells No. 56, No. 51/N0. 54, No. 60 and No. 59, but 

 has not so far yielded a very large quantity of petroleum. Only in 

 one well No. 54, but perhaps also in No. 13, a sixth oil sand seems 

 to have been found below the fifth horizon, but no details can be given 

 about its extension. As no samples of petroleum have been obtained 

 separately from either the fifth or sixth oil sand, nothing can be 

 said about the specific gravity of the petroleum they contain. 



So far the few wells which went deeper than the fourth oil sand 

 seem to have proved that the lower sands contain only a small 

 quantity of petroleum. Whether this applies also to still deeper 

 strata remains to be seen, and nothing definite can be said at present, 

 and only an actual boring can decide. 



It will be useful to record in this section a few more observations 

 which are intimately connected with the occurrence of the petroleum. 

 These are : The migration of the petroleum within the beds in 

 which it is contained at present, and the relations between the occur- 

 rence of gas, petroleum, and water within the whole series and 

 within a single bed. 



Although the assumption that the petroleum has migrated from 

 other places to the beds in which it is contained now, must be 

 rejected for very strong geological reasons, it cannot be denied 

 that a certain amount of migration must take place within the 

 petroliferous bed itself. In fact, it would be difficult to believe that 

 the petroleum remains in an absolute state of rest inside its recep- 

 tacle. There are two facts which almost prove conclusively that 

 a certain amount of movement of the petroleum must take place. 

 These facts are — 



(a) The periodical rise and fall of the production with the season. 

 (4) The continuity of the production of the deep wells. 



(a) The periodical rise and fall of the production during the 

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