YUKON PLACER FIELDS. 121- 
OPEN-CUT MINING. 
The ground is generally stripped first of all by sluicing off the overlying muck. A bed- 
rock drain is then constructed, and an open cut of sufficient width for one or two sets of 
boxes is carried gradually up the valley. In some cases the gravel is hoisted by steam power 
entirely out of the cut to boxes set above the surface and to one side of the workings. By 
this method a frequent resetting of the boxes is avoided and there is a better disposal of 
tailings. Gravel is hoisted by derrick, by automatic trolley, or sometimes by a rock pump. 
When the last method is used a set of boxes is placed on the bottom of the eui , I lie coarsest 
pieces are forked ut, and all the rest of the material is elevated through the pump to the 
boxes on the surface. Owing to the depth of the gravels, the open-cut method and its modi- 
fications are of limited application. 
The methods of working the deep gravels of this region may be said to be like those 
employed in the deep gravels of other fields, but with modifications rendered necessary by 
the frozen character of the ground. These methods have gradually developed in the Yukon 
territory and in Alaska and from year to year have become of increased efficiency in solving 
the problems that are met. In the Fairbanks region till within the last two years thawing 
was accomplished by the crude methods already mentioned, and the equipments for thawing 
by steam, which had been found so effective in the Klondike region, were not plentiful. 
Since then extensive steam plants have been introduced, capable of thawing and handling 
daily large quantities of gravel. 
The process in general includes the following operations: (1) The sinking of a shaft to 
bed rock, ranging in depth from 20 to 120 or more feet; (2) the timbering of the shaft and 
the portion of the drifts near the shaft; (3) the opening up of the ground by drifts which 
are run either parallel to or across the pay streak and from which crosscuts are driven; (4) 
the extraction of the gravel from the crosscuts, beginning at the farther limits of the drifts 
and working toward the shaft; (5) the hoisting of the pay gravel with as little waste as pos- 
sible to the surface, and (6) the recovery of the gold by ordinary sluicing. The main drift 
is usually carried to a maximum distance of about 200 feet in each direction from the shaft, 
and the ground is blocked off by crosscuts having a variable length up to about 100 feet. 
Fortunately, but little timbering is generally required. Where the ground is weak, pillars 
are left at intervals of about 25 feet when working back the faces. Ordinarily, as mining 
commences at the extreme limit of the area to be worked, the ground from which the pay 
dirt has been removed is allowed to settle if it will. Experience has shown that settling is 
generally so gradual that the work can be carried away from the settling ground with suf- 
ficient speed to avoid trouble. 
The steam-point method of thawing is the one most commonly in use. The steam point 
is a piece of one-half or three-eighths inch hydraulic pipe, 5 to 8 feet or more in length, with a 
blunt, hollow point of tool steel for piercing the ground and a solid head of tool steel or 
machine steel, sufficiently strong to withstand the impact of a mallet or sledge. Steam is 
admitted through a pipe fitted laterally in a small aperture near the head. The points are 
placed about 2\ feet apart and from a dozen to twenty or more are used in a plant of average 
size. The power needed is 1 to 2 horsepower per point and the duty of a point is 3 to 4 or 
or more cubic yards per day of ten hours. In use the point is driven in gradually as the 
ground becomes thawed. It is customary in most cases to use either hot water at ;i tem- 
perature of about 140° F.or a mixture of hot water and steam while driving the points, and 
then to complete the thaw by means of steam alone, since by employing hot water in a pan 
of the operation the atmosphere of the mine does not become so vitiated through the con- 
densation of the steam and the conditions for working are consequently better. 
Hot-water hydraulicking by means of the pulsometer or other steam pump has been 
found very successful in some cases. Pulsometers were in use which were reported to do 
the work of 20 points, and as by this method a jet of hot water is thrown forcefully againsl 
the frozen face, the conditions are more favorable for the release of the gold particles from 
