70 GRAVEL AND PLACER MINING IN ALASKA. [bull. 263. 
which catches any gold that may have passed the preceding string. 
Such an arrangement, though of considerable use when gold is gener- 
ally coarse, will not serve when fine gold is encountered. An under- 
current of greater surficial area and greater grade, carrying the water 
in a thin sheet, would then be demanded. 
In washing the gravel 150 miner's inches are used. The water is 
brought from Ophir Creek in a ditch 1£ miles long. It is 6 feet onj 
the bottom, 9 feet on top, and has a grade of one-tenth inch to 100.1 
feet. It cost $8,000. 
Tailings are handled by a derrick and a self-dumping scraper. 
Power is supplied to the latter by hauling directly from the derrick 
boom, and its operation is directed by two men. In this case the der- 
rick leans toward the dump pile, to which it carries its load by gravity, 
being hauled back by the steam winch. To the scraper is attached a 
rope which, on tightening as the derrick swings, dumps the load at itsj 
destination. . (See PI. X.) Both the derrick boom and mast are lOj 
feet long and are arranged like the excavation derrick, except that] 
the mast leans in the opposite direction. A 15-horsepower boiler and] 
8-horsepower winch are used, and there are three men on each shift. 
The tailings derrick is not occupied more than one-fourth the working 
time of the pit derrick. 
In all from 55 to 60 men are employed about the plant. A man is] 
continually needed at the mud box to trip the bucket and to feed tfl 
gravel as regularly as possible to the sluices from the platform. A 
winch man is needed at each derrick. A man in the pit devotes his 
entire attention to the snubbing line, while two men are necessary ori 
the scraper. The latter feature could possibly be improved by some 
mechanical method not requiring the hand labor. Wages are 50 cents 
an hour, with board, and work is continued eleven hours each shift. 
Besides the derrick plant above described another, seen on Ophir 
Creek, made use of iron skips of li cubic; 3^ard capacity, which werej 
run on trucks to the working face and, after loading, were trammed 
within reach of the derrick and lifted to the sluice. As nearly as- 
could be learned, while the capacity of this plant was from 15 to 20 
per cent higher than the one previously described the work was not 
being done so cheaply. In the last case it was necessaiy to pump the 
seepage water from the pit, while in the first case all seepage water 
was naturally disposed of by draining into the peculiar cavernous 
limestone bed rock. In derricking plants in general, large rather 
than small buckets or skips are to be recommended, but the various 
elements of the plant should be so coordinated that the capacity of 
the derrick is not above that of the shoveling and tramming or of the 
sluice. 
The derricking plant seen on Pedro Creek, in the Fairbanks district, \ 
has been described in connection with the method of using* the cable 
