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Drilling to test the depth and gold values of possible drifting or dredging
ground was first done in the area about 1895, with an “hydraulic jetting
machine.” Casing was used, and water was forced down the drill stem and
up the inside of the casing. Some excellent work resulted in determining
the depth of the ground, especially at La Fontaine on Lightning creek, but
apparently no reliance was placed on this method as an indication of the
gold values. Indeed, some of the most disastrous failures in drift mining
were due to the fact that the gold values were not determined before mining
was undertaken. Only during the past ten or fifteen years has it been
generally recognized in the district that the drill is one of the most effective
and cheapest means of testing the ground. Small portable Keystone or
Standard drilling rigs, and occasionally hand drills, have been used in
recent years, and much of the ground has been tested. Comparing the
gold values as determined by drilling with those later obtained by extensive
dredging in California, Alaska, and other places, it is now generally conceded
that “Employing the outside diameter of the casing as a basis for calculating
the volume of the core has been found in practice to give high results. A
pipe formula reducing the value of these results, and based on check shaft-
tests made by W. H. Radford, has been generally accepted. This formula
reduces the results obtained by the theoretical formula about 144 per cent.
In its simplest form it is as follows:

Value of gold obtained & 100

Value of gravel per cub. yd. =
Depth of hole in feet

When drilling has been carefully done, 75 to 80 per cent of the estimated
yield can be recovered by the dredge. This includes all losses, not only
those in the tailings, but unrecoverable islands and corners left behind in the
course of operations. In Alaska, however, where the ground is shallow, the
gold coarse, and on a shattered bedrock, dredging results have usually
exceeded the estimated yield, the percentage of recovery being from 103 to
198. When these high recoveries have been obtained, the dredging depth
has always been greater than the drilled depth, in cases as much as 30 to
40 per cent.”! Drilling in Barkerville area in 1915 cost the Yukon Gold
Company about $2.50 to $3 a foot. Other recent drilling has cost con-
siderably more, probably nearly $5 a foot.

Dredging has only recently been undertaken in the area. The costs
are estimated at 10 to 11 cents a cubic yard, or somewhat greater than the
cost of hydraulicking, but this is largely offset by the fact that dredging can
be carried on for about ten months in the year, whereas the average hydrau-
lic season is only about five and a half months.

The cost of constructing ditches in the area varies from $2,000 to
$5,000 a mile depending upon the size of the ditch, the amount of rock
work, fluming, etc.

CLIMATIC CONDITIONS AND WATER SUPPLY

Records of climatic observations at Barkerville are available? from
1888 to 1924.

s 1Haley, Charles Scott: ‘‘Gold Placers of California’; -Cal. State Min. Bur., Bull. No. 92 (1923).
2Reports of Meteorological Service of Canada, Toronto, Ont.

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