PLACER GOLD OF THE BARKERVILLE AREA. 561

parts of the veins may be explained partly in one way and partly
in another. From the relatively insignificant amount of lode
mining, resulting in the recovery of only a few thousand dollars
worth of gold, specimens of free gold of a maximum weight of
at least 1/2 ounces have been found. From the mining of at
least thirty millions of dollars of placer gold, representing the
concentration from the wearing away of a great thickness of the
country rock and veins, there is said to have been obtained only
one or two nuggets above thirty ounces in weight. Lack of ex-
ploration of the ledges, therefore, may be partly the reason for
the failure to find any but small amounts of coarse quartz gold.
During the time when the country was being reduced to a plain,
conditions were probably very favorable for gold enrichment in
the upper parts of the veins. The gold thus formed and released
by weathering gravitated into the old valleys in the plain. Re-
juvenation of the streams by uplift caused a further concentration
in valleys, which coincided nearly with the ancient valleys. This
concentration has produced the present placers. The free gold
in the outcrops on the plateau represents the roots of the ancient
enriched zone, the upper parts of which were removed to the
streams. Most of the vein enrichments which produced coarse
gold in the past have thus undergone two concentrations in the
stream beds, leaving only a small part of these enrichments: for
exploration today. Ice-erosion during Pleistocene time also re-
moved parts of the enriched zone. It is, therefore, not to be ex-
pected that the present outcrops of the veins would be as rich in
free gold as were the ancient outcrops. There is every reason to
suppose that, if the oxidized parts of the veins could have been
examined before the plain-like surface of the region was uplifted
and dissected, rich bonanzas of free gold would have been en-
countered.

GEOLOGICAL SURVEY,

OTTAWA, CANADA.