YENANGYOUNG. 93 



some of the minor beds represent but local horizons within the 

 stratigraphical series. With the above restrictions I have adopted 

 the following sequence of strata: 



(a) Immediately below the Yenangyoung stage follows a thin 

 bed of blue clay which apparently represents the upper portion of 

 the Prome stage. So far this bed has only been found in well 

 No. 55. It is extremely difficult to say whether this bed is also 

 represented in such wells as Nos. 3, 8 or 36, where a sequence of very 

 thin beds of clay alternating with sandstone has been found imme- 

 diately below the Yenangyoung stage which is usually designated as 

 "shale." The probability is decidedly in favour of this view. 



{b) Below the above bed follows the first oil-sand, which contains 

 only traces of oil in wells Nos. A and 21, in all the other wells it is 

 either dry or carries water. The first oil-sand, however, may in 

 its turn follow immediately below the Yenangyoung stage, without 

 the separating medium of clay (a) being present. Instances have 

 been recorded in various wells ; as No. A, No. 40, etc. 



It is impossible to say whether in such instances as well No. 3 or 

 No. 23 the "slate and sand " immediately below the Yenangyoung 

 stace represents the first oil-sand ; it is, however, highly probable, 

 because, in the quoted instances, they have been discovered in the 

 same position as the first sand in other wells. 



(c) The first sand is usually followed by a bed of clay of varying 

 thickness ; it is very probable that the first two beds are occasion- 

 ally absent, and that this bed follows immediately below the Yenang- 

 young stage ; at least some of the boring registers cannot be inter- 

 preted in any other way. 



(d) The second oil-sand follows, as a rule, below the above men- 

 tioned clay, but, as in the case of the above mentioned beds, there are 

 instances which render it very probable that the upper strata are 

 entirely absent, and that the second oil-sand follows immediately below 

 the Yenangyoung stage. In thickness it varies a good deal and the 

 record of No. 68 suggests the idea that in this instance the separating 



( 139 ) 



