64 GRAVEL AND PLACER MINING IN ALASKA. [bull.2( 
operations. In only very exceptional cases should the expense < 
handling, after the material is once dumped from the scraper, 1 
allowed to exceed 5 cents to the cubic yard. 
The plant above suggested implies the use of a scraper of lar^ 
capacity and should handle the gravel at a total cost, including depr 
ciation charge and added cost of stripping, not to exceed 40 cents p< 
cubic yard in Alaska, provided that 700 cubic } r ards of gravel a ds 
are sent to the sluice. In order to accomplish this a scraper, prefer 
bly of the bottomless, self -dumping type, of 6 yards theoretical capa 
ity, should be used. It will be found that actually 3£ yards will 1 
delivered each time by such a scraper. The operations will require 
60-horsepower boiler and doable-drum hoist, and the services of sev( 
men on a shift. The total running expense of the plant should a 
exceed $150 a day of 24 hours. 
The double-drum hoist operating the scraper will have a position c 
the side of the sluice opposite that of the cut, and can be mount< 
on skids so that it can be easily moved by means of a sheave and dea< 
man if necessary. The sheave through which the drawback cable rui 
may be anchored to a weighted car running on 200 feet of track la 
parallel with the cut on the side opposite that occupied by the slui< 
and hoist. If it is desired to keep the drawback cable out of the w* 
it may pass through two sheaves, one anchored to traveling anchor ai 
one to deadman, the cables thus forming a triangular arrangemen 
two of whose angles will var}^ as the car is moved to cover varioi 
parts of the ground. The car may be moved as often as desired, ai 
thus one furrow after another may be made by the scraper over a ti 
angular area as the ground thaws. By means of a rearrangement > 
the sheaves it is found that nearly all of the ground can be covere 
A plant erected for the Klamath River Gold Mining Company a is pr 
vided with two li-yard scrapers, which travel back and forth alte 
nately, both cables acting as pulley and drawback cables. Two sheav 
are used on the side of the excavation opposite to the washing plar 
" These sheaves are attached to a spreader which keeps them spaced 
given distance apart, and to each end of the spreader is attachec 
tackle which runs back at an angle to deadmen to which they a 
securely anchored." 
The type of bottomless scraper shown in fig. 8 (p. 65) was seen 
successful operation stripping loam at a reservoir excavation ne 
Portland, Oreg. It has a theoretical capacity of 6 yards, and actua I 
handles a little over half this amount. Measurements of a spoil ba i 
showed that in seven ten-hour days, stripping to 4 feet in depth, 4 
cubic yards per shift had been handled. The scraper was maki i 
furrows over 300 feet in length. A 60-horsepower boiler was us< ( 
a Yeatman, J. A., Automatic excavator for placer mining: Min. and Sci. Press, Dec 17, 1904. 
