78 Professor Henry A. Miers [Feb. 28, 



the bottom of the shaft, caught by a travelling clutch, carried along 

 a horizontal rope to the dump-heap or the sluice- boxes, where it is 

 automatically tilted. All this is done by an engine in charge of one 

 man, and saves much labour. 



As regards the washing of the gravel, the old-fashioned hand- 

 rockers are still to be seen in operation upon many of the gulches, 

 but have been for the most part replaced by sluice-boxes. These are 

 long wooden troughs made in 12-foot lengths and about 10 inches 

 broad ; the bottom is lined with wooden riffles, consisting generally 

 of longitudinal bars (Pole riffles), but sometimes of transverse bars 

 (Hungarian riffles), by which the gold and heavy minerals are caught. 

 Sometimes Auger riffles — planks with circular holes — are employed ; 

 mercury is seldom used. A sluice-head of 75 miners' inches, i.e. 

 112 cubic feet of water per minute, is usual, and a fall of about 

 8 inches in the 12-foot box length. 



Water, which is very scarce in the district, and must be used 

 economically, is conducted to the sluice-boxes by long wooden flumes, 

 which are themselves a serious expense on account of the cost of 

 wood (about $110 a thousand feet). Some of these flumes are half- 

 a-mile in length ; in a wide valley, where the pay-streak is on the 

 opposite side from the stream, it is necessary to raise it by centri- 

 fugal pumps to a height of 30 or 40 feet, and to convey it across the 

 valley by a long flume. 



In the final " wash-up," by which the gold-dust is extracted from 

 the sluice-boxes, the riffles are taken out, and a copious stream of 

 water is sent down, which carries away the fine gravel and leaves the 

 gold, and a heavy black sand which accompanies it. This black 

 sand consists mainly of magnetic ore, and it is removed partly by a 

 magnet and partly by shaking with the hand and blowing with the 

 mouth in a small metal tray. 



The mining operations on the creeks and upon the hill-sides are 

 somewhat difi'erent. On the creek a shaft is sunk down to bed-rock, 

 four lateral tunnels are driven from the shaft along the surface of 

 the bed-rock, and opened out in a fan-like manner to the limits of 

 the claim. The outermost portions are worked out first, and as the 

 excavation is carried back to the shaft, the roof and overlying muck 

 are allowed to cave in and settle down on to the bed-rock. Timbering 

 is thus entirely avoided. This absence of timbering in the Klondike 

 shafts and tunnels is one of the most striking features in the mining ; 

 the frozen ground requires no support — it never thaws — and chambers 

 as much as 100 feet square are covered by an icy roof which never 

 breaks down. 



The operations in the creeks are carried on upon a very consider- 

 able scale, and there is a large amount of machinery in the country ; 

 upon some groups of claims the work is not carried on by sinking 

 and drifting, but is more of the nature of open quarrying. Night 

 work is prosecuted by electric light or the acetylene lamp. 



Formerly the raising of the gravel and its storage in dumps were 



