YENANGYOUNG. 



83 



continuations of the vertical veins, injected into the surrounding 

 beds. There is no doubt with regard to this mode of occurrence at 

 another section, but in this particular instance it is quite clear that 

 the horizontal beds (b) existed before the vertical veins (v) passed 

 through them. 



As to the shape of the veins themselves there is not much to be 

 said ; they apparently represent a network of fissures varying from 

 the thickness of a sheet of paper to about ten inches. The veins 

 remain sometimes independent, two or more may join, or lateral 

 offshoots may branch off and continue to run as independent veins. 



Another and perhaps better illustration of this feature is the 

 occurrence of mud veins near well No. 510 in the Berne part of the 

 Yenangyoung oil field represented in the following woodcut. We 

 see here an almost horizontal bed of eruptive mud (a) imbedded in 



Fig. 6. Diagrammatic section snowing diagonal veins of eruptive mud in miocene 



sandstone, near well 310. 



soft, horizontally stratified sandstone. This mud deposit sends off 

 several offshoots, of which (5) may perhaps be doubtful, whilst (<:), 

 (d) f and (e) are good examples of such veins. The offshoots (c) are 

 particularly interesting, as they exactly resemble the apophyses of 

 an intrusive rock and are unquestionably injected into the surround- 

 ing matrix. 



The most interesting offshoot is however (d). It branches off the 

 main vein at about 70 , keeps to that direction for about 3 feet, then 

 suddenly forms a knee, and follows the bedding of the sandstone, 

 G2 ( 129 ) 



