Chance.l ^^^ [July 15, 



ground, is : Can these deposits be profitably worked by hydraulic mining? 

 The question may be answered both in the afiBrmative and in the negative. 

 At a few places where the gravel is both rich and thick — ten feet or 

 more — and water can be obtained in sufficient quantity at moderate cost, 

 hydraulic mining may be successful — but 



1. A large working area is necessary. 



2. The closest economy must be exercised, and 



3. A relatively small amount of capital invested. 



A large area is necessary, because the deposit is not thick ; assuming an 

 average thickness of four yards, one acre would yield but 19,360 cubic 

 yards of gravel, and one-fourth of this being top gravel and soil might 

 contain very little gold, as the gold is often concentrated in the lower 

 layers, sometimes in a "pay-streak," near the bed-rock. This "pay- 

 streak " is at times quite thin — one, two or three feet thick, but the gold 

 is more visually disseminated through the mass. 



The difl'erence between the cost of working these thin deposits, and the 

 enormously thick gravels of California and Oregon will be readily ap- 

 preciated by the hydraulic engineer, and to this difference is due the fact 

 that although these gravels are much richer than many Western deposits 

 successfully worked, the prospect of remunerative mining in this region is 

 much less. 



In some localities the cost of bringing water will be very great ; ditches 

 ten or twelve miles long being necessary. At the Sam Christian mine, on 

 the Yadkin river, arrangements are even being made to jyump the water ! 



It will also be difficult to obtain sufficient fall to carry off the tailings, 

 for some of the richest of the hill gravels has been found in comparatively 

 low ground, where much of the material must be moved by hand. I 

 noted one mine working under just such conditions, that was yielding as 

 well as the best can be expected to average. The gravel was about four 

 yards thick, the gold occurring principally in a pay-streak near the bed- 

 rock. The lowermost four or five feet was moved by hand, some pick 

 work being required. 



The cost for labor was about 64 cents per superficial square yard, and 

 the yield averaged over a considerable area one pennyweight — 85 cents. 

 Labor 75 cents per day. This shows a profit of 21 cents per superficial 

 square yard or 5.25 cents per cubic yard ; but these figures do not include 

 the cost of superintendence, mercury, wear and tear, etc. When these 

 items are included, it can easily be seen that the operations were being 

 carried on at an actual loss, for not more than one hundred yards were 

 washed per diem, and the profit on this would not pay the expenses of 

 management. 



A trial of General Strong's injector dredging machine* is now being 

 made on the gravels in the bed of Silver creek. It seems better adapted 

 to working on river bottoms than on these small South Mountain streams. 



* Described by Dr. R. W. Raymond, in Vol. viii, Transactions of the American 

 laslitute of Mining Engineers. 



