MINING METHODS. 321 



practically verbatim from his paper, as it is felt that they merit the 

 further publicity which they will obtain herein. 1 



Suitability of the gromd.— Having decided that the quantity 

 and value of the ground is suitable for sluicing, the percentage of 

 boulders and stones, over say 3 inches in diameter, should be deter- 

 mined by picking them out of the prospecting pits, stacking in a 

 regular heap and comparing the volume with that of the pit. A 

 rough rule for estimating the effect of these stones in subsequent 

 operations is to add 1| annas to the cost per cubic yard for each 

 10 per cent, of stones. Particular care should also be exercised in 

 looking for the presence of hard bands of laterite, cemented gravel 

 or tough clays. 



Available water.— The source of the water supply should then 

 be most carefully studied and unless a very large excess is 

 available, no considerable expenditure of funds should be incurred 

 until a series of measurements extending over at least one season 

 has been made. The streams in the Tavoy district are most decep- 

 tive, and roaring torrents impassable in the rains shrink to nothing 

 in the dry season. A measuring weir should be constructed in the 

 chosen stream and extra attention paid to measurements in the dry 



weather. 



The next matter to be decided is what constitutes sufficient 

 water. This depends on the extent, character and richness of the 

 ground and Mr. Lyons believed that a fair average figure for the 

 district was that one cubic foot per second under sufficient pressure 

 would break and carry away 100 cubic yards daily. Thus, if an 

 average of 750 cubic yards daily over a period of, say, 5 months 

 has been decided on as being the smallest that it would be profitable 

 to treat, the average water must not be below 1\ cusecs. When 

 the water available falls below U cusecs, it is better to revert to 

 some form of hand working. 



Disposal of tailings.— On low ground the disposal of tailings is a 

 difficult matter and contoured plans of the area should be made. 

 Sections showing the natural surface and also the bed rock as revealed 

 by borings or pits should be prepared, and on these a line representing 

 the tail race should be plotted. It should start at a sufficient eleva- 

 tion above the valley into which the tailings are to be discharged to 

 allow for the accumulation of a large, amount of material. Stony 



1 C. M. Lyons (17), pp. 45-54. 



L2 



