tURiNGToN.] SLUICES AND GOLD-SAVING APPLIANCES. 199 
In the construction of washing plants of a larger and more expen- 
sive kind, the operator has the benefit of the experience developed in 
gold dredging. This now rather important industry has brought into 
service devices for gold saving, in the use of which one of the main 
objects is to utilize to the best advantage all available vertical and 
areal space. 
The employment of large mechanical excavators for placer mining 
has a held in the Northwest. Such operations necessitate one or more 
permanent washing plants to receive the gravel from each machine. 
It has been demonstrated that the dredge is the only form of exca- 
vator which can economically transport its sluices as it moves. 
Therefore a plant, situated as safely as possible with reference to 
danger from floods, and economically with reference to tramway, 
dump, and water supply, must.be constructed frequently at a consid- 
erable expense. 
The shaking screen, although it has received a thorough trial on 
gold dredges, does not find as much favor as the trommel. It is not 
impossible that modifications of the principle of the shaking screen 
and of the shaking table may be developed which will act more effi- 
ciently in saving gold than the trommel. Mr. Felix Francois a has 
recently figured and described a " shaking sluice-box " system of gold 
saving, for installation either in stationary washing plants or in 
dredges. He claims a very high percentage of saving, and as addi- 
tional advantages the elimination of the use of quicksilver and the 
employment of a small amount of water. He does not give the cost 
of the plant, however, nor any actual results of its operation in practice. 
The use of the trommel in a stationary washing plant is illustrated 
in PI. XII, A (p. 80), a plant erected in the Klondike in connection 
with a steam shovel and incline operation. A short description of 
this plant is appended, but it should be understood that for the average 
miner the installation of such a plant is impracticable on account of 
first expense and the difficulty of getting the complicated machinery. 
The plant used 125 miner's inches of water, led by a ditch from Bear 
Creek; the capacity was said to be 500 cubic yards in ten hours. The 
material elevated to the platform at the upper end of the trommel was 
dumped into a hopper feeding the trommel. The water was led into 
the lower end of the trommel and fed through a perforated pipe. The 
largest holes in the revolving screen were 1 inch in diameter, and all 
oversizes passed through and into the hopper below the lower end, 
whence the tailings were hoisted in a self -dumping carrier, on a cable, 
for a horizontal distance of 200 feet and a vertical distance of 60 feet. 
The fines passed over 80 square feet of riffle tables, floored with 
expanded metal and cocoa matting, on a grade of 12 inches to 12 feet, 
followed by sluices with iron Hungarian riffles. PI. XII, i>, shows the 
a Bull. Soc. de 1* Industrie minerale, vol. 3, 1894, p. 785. 
