DETAILED ACCOUNT OF SOME RECENT EXPERIMENTS. 63 



certain point on the banks of both the Rangoon river and the 

 Poozoondoung creek, all the wells contain more or less brackish 

 water shows that there is very free underground communication, 

 and that " there is a continuous outflow from the outcrop of the 

 gravels to the sea," the permeable sands not being perfectly en- 

 closed by watertight strata. 



Mr. Oldham gives the following description of the method by which 

 the wells were sunk : — " they are cased with iron piping of from 

 2\' to 4* internal diameter, which was sunk by the simple process 

 of forcing a stream of water down a smaller tube of from 1" to 2" 

 bore, inserted in the centre of the outer casing. The stream of 

 water ascending the annular space between the two tubes carried 

 with it the material washed from the bottom of the bore, and so 

 enabled the two tubes to be sunk simultaneously ; when the well 

 was completed, the inner tube was withdrawn and a pump attached 

 to the outer one. This process appears to be simple, inexpensive, 

 expeditious, and effectual, though of course only applicable in soft 

 and not too coarse grained deposits, but it has an effect on the stuff 

 washed out that must be allowed for. The stream of water which is 

 sufficient to wash away fine clays or sands, would be insufficient to 

 bring up coarse grit and small pebbles to the surface. Consequently 

 if pebbles are mixed with fine sand or clayey matter, the stream, 

 which has sufficient power to bring the pebbles to the surface, will 

 wash away all the finer matter, and so what would seem to be a 

 clean gravel, to judge from the washed material brought up, might 

 really be a mixture of pebbles and clayey sand, of very little value 

 as a source of water. " 



With respect to the boring records appended below, Mr. Oldham 

 makes the following remarks : — 



" Most of these sections have been preserved in glass fronted boxes, in which 

 the different layers are arranged one above the other. In some cases this has 

 been done to scale, and there was no difficulty in determining the depths and 

 thicknesses, in others no fixed scale was followed, and the depths are indicated by 



( 63 ) 



