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Page:Popular Science Monthly Volume 61.djvu/240

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234
POPULAR SCIENCE MONTHLY.

The gold is very unevenly distributed in the gravel. The richest patches of pay-gravel seem to occur about half way down the valley. In the wider portions of the valleys the pay-streak may be sometimes on one side and sometimes on the other, following no doubt the former course of the stream.

The valley gravel is generally from ten to thirty feet thick, and is overlaid by from five to fifteen feet of frozen bog, locally known as 'muck.'

The hillside gravel is a very remarkable deposit; it consists almost entirely of boulders and pebbles of quartz and of sericite-schist, and, when it is exposed to view, presents the appearance of a uniform white ledge running horizontally along the hillside at a height of about 700 feet above the level of the Klondike River. It sometimes attains a depth of 120 feet, and may be as much as half a mile wide. The pebbles are to a large extent subangular and less worn than those of the valley gravels.

The early miners of course confined their attention to the valleys, and the discovery of these rich deposits upon the hillsides excited great surprise; they now rival the valley gravel in importance. The deposit is locally known as 'white-wash' or the 'White Channel.'

The origin of the White Channel is shrouded in mystery; it was at first supposed to be a glacial deposit; but there are no striations or other signs of glacial action, and it is now the opinion of the local geologists that it was laid down by the sudden inrush of tumultuous streams acting over a small area. The materials have clearly not been transported far, and the gold is even more nuggety and less worn than that of the valleys.

One is naturally led to inquire whether all the gold of the lower gravels was not brought down by streams cutting through the White Channel which occupied the bed of the valleys when they were broad and shallow, so that the White Channel may be the real source of the gold. This view is supported by the fact just mentioned that the gold of the valleys is more worn than that of the hillside, also by the fact that the valleys are richer in their central portions, which must have been covered by the White Channel, than in the upper parts which are above the level of that deposit.

Still there is no reason to doubt that the White Channel itself is of local origin: its materials are those of the district, and have not traveled far. (There are a few gravels in this area which consist of pebbles foreign to the district, and they are not auriferous.) The White Channel itself follows the present valley courses. On the whole therefore although the origin of this peculiar deposit is obscure, there can be no doubt, in my opinion, that the conclusion forced upon us by a glance at the map is correct, and that the gold has been derived from