TRANSACTIONS OF SECTION C. 593 



parallel strata. As work profrress&s in depth on the Main Reef it will be found to 

 fliitten, or have a decreasinj^ dip from the horizontal, and tlien to become horizontal, 

 and perhaps risinfj to the surlace, thus f'orminir the southern rim of the basin. 



As j'et no developments liave been made to indicate the vertical distance be- 

 tween the Main and Black Reefs. Many intermediate veins liave been found 

 between these two ; some of them can be worked proKtably. The first work in this 

 district was done on the Main Reef, and consequently it is more developed than the 

 others. It has been very tlioroutrhly worked and prospected for -M) miles in length, 

 and fairly prospected for GO miles more. With exceptions of a few faults (forming 

 a very small percentage of the whole length), the present development in uniform 

 and continuous pay e,s- over 25 miles long, icith every prospect of being found to be 

 much longer. 



The so-called Main Reef is composed of four parallel veins within workable 

 distance of each other, aggregating about 15 feet in thickness, the Main Reef being 

 about lialf of this; the average yield in gold varying from 8 pennyweights in 

 the Main Reef to 8 ounces in the Robinson leader to the ton. The monthly 

 variation in the average yield per ton in the crushings reported by individual mines 

 is caused by varying the proportions of ore from the different veins. A larger 

 amount from the rich leaders will cause a higher average, or a larger amount from 

 the Main Reef will cause a lower average. The variation in the monthly yield is 

 not caused, as many suppose, by change in tlie yield of the vein : each vein is fairly 

 uniform when compared to itself. The JIain Reef veins have been worked for 25 

 miles in length and to a depth of over 200 feet, and, witli some few exceptions, have 

 been found uniform in size and yield. At present there are about 800 stamps 

 crushing ore from the Main Reef mines, crushing about 40,000 tons, and yielding 

 about 30,000 ounces of gold monthly, which gives an average yield of three-quarters 

 of an ounce of gold per ton of ore; this can be taken as the present average yield of 

 the Main Reef, which will probably be largely increased as improved appliances for 

 saving the gold and better management are adopted. 



Owing to bad mining and milling in manj' mines (though some are very well 

 managed), the present average expense of minuig and milling is probably 30«. 

 per ton. Estimating the gold at its market value of 31. 10s. per ounce, this gives : — 



£ s. d. 



Average yield of ore per ton 2126 



Less estimated expenses as now worked . . . 110 



Net profit per ton at present . . . . 12 6 



This profit will probably be increased to 21. by saving more gold and economies 

 in the working cost, resulting from better arrangement. ' 



These figures make the present value of each acre of ground underlaid by the 

 Main Reef at an angle of 25 degrees, worth over 45,000/. net profit, with a strong 

 probability of being soon doubled, as better work is done in mining and milling ; 

 this amount will also increase with the dip of the vein, in consequence of in- 

 creasing the tonnage per acre. 



The Black Reef vein is being worked in many places, and has been traced for 

 a great many miles. It averages 3 feet thick, and yields in the ' Black Reef mill 

 16 pennyweights of gold per ton. The total cost of mining and milling this ore is 

 less than 2Qs. per ton. 



The Zuur-Bult vein averages 3i feet thick, and yields 1 ounce of gold per ton, 

 at a total cost of mining and milling of less than' 20*. per ton. These two last 

 veins are the top or upper veins of the basin ; as they lie very flat and level, and can be 

 very cheaply worked, they promise to be important gold-producers in the future. 



The richness of the mines of this district will be seen by comparing them with 

 other mines. For example, take the Alaska Mining and Milling Company's mine, 

 at present the best dividend-paying gold-mine in the United States. The following 

 is the working for the six months ending June 15, 1889 :— 



108,000 tons crushed , average yield per ton . . . ^3.80 

 Average cost per ton of mining and milling . . . /1. 89 



Average net profit per ton ^1.91 



1889. Q Q 



