52 GRIMES : MYINGYAN, MAGWE AND PAKOKKU DISTRICTS. 



least six miles to the south and four-and-a-half miles to the north, 

 the first oil sand of the lower miocene at its crest is within 350 feet 

 of the surface of the ground, and as the places where the Signal hill 

 sandstone disappears are amongst the hills, the crest of the first oil 

 sand is at a less depth below the level of the Irrawaddi river, espe- 

 cially in the case of the northern extension. The area which can be 

 exploited with any good chances of success does not extend far north, 

 and also narrows rapidly both to the north and to the south. Taking 

 well No. 6 as on the edge of the exploitable area, as it is the farthest 

 west, and yields only a small quantity ofjjoil ; and then, by means of 

 mapped Signal hill sandstone, finding places in the other blocks 

 where the first oil sand is at the same depth as in this well, I have 

 been able, by joining up these places, to trace a line on the west side 

 of the anticline, which is an* approximate limit of the area within 

 which the oil can be exploitedjwith hopes of success. This line can 

 only be regarded as "approximate, as we do not know if the small 

 yield of oil in well No. 6 may not be due to some local cause, or to 

 the same influences which have acted in the case of the other wells 

 sunk at the bottom of the Chaung ; and also there is no means of 

 knowing what variations there are in the thickness of the beds 

 between the Signal hill sandstone and the first oil sand of the Prome 

 stage. The line, however, will, I think, be found to be fairly correct 

 as a limit, but, if anything, it is more likely to be a minimum than a 

 maximum limit. Tracing this line to the south we see that the ex- 

 ploitable area rapidly becomes narrower owing to the sinking of the 

 anticlinal arch, but the crest of the anticline itself sinks somewhat 

 less rapidly, as the downward movement of the anticline as a 

 whole is, near the centre, partly compensated by a narrowing of 

 the arch and consequent increase of dip, which brings the crest itself 

 higher and so nearer the surface. A continued sinking, however, 

 makes the area very narrow in block 12, and in the northern part of 

 block 13, about three miles south of Yenangyat, it dies out. North of 

 Yenangyat we find a similar contraction, and the area ends in the 

 ( 52 ) 



