150

of water would have to be pumped in order to drain the ground, but it is
evident that a much larger pumping plant than the one used would be
required.

Pay-gravels were struck in one or two of the bore-holes north of the
creek at a depth of 83 feet from the surface. The gravels have a thickness
of 12 or 13 feet, but what the values amount to is not known. They
evidently form an interglacial pay-streak, for they are overlain and under-
lain by glacial deposits. The width of the pay is probably not over 100
feet, for it does not seem to have been struck in more than one or two of the
bore-holes. The gravels may be of some importance as a dredging possi-
bility, for they probably extend for some distance up and down stream
from the mine, but the values in the gravels would have to be fairly high
to pay for dredging, because of the nearly barren overburden. The gold
values in the gravels resting on bedrock in the deepest part of the channel,
according to the few tests made by washing the gravel obtained by breaking
into the channel, were found in one test to amount to 7% pennyweights a
cubic yard and in another nearly one ounce to the yard. In both cases,
however, less than a yard of gravel was tested. These values are much
less than those found in the early days in the bed of Williams creek and at
other places in the region, and unless the true values are higher and extend
throughout a considerable thickness of the bedrock gravels, it is doubtful
whether the gravels would pay for mining under present conditions, assum-
ing that it be possible to drain the ground sufficiently to permit of mining.
It is true that mining of bedrock gravels by drifting was done twenty-five
years ago at La Fontaine mine, on Lightning creck, at a cost of $3 or $4 a
yard (actual mining cost not including overhead), but at that time fuel and
wages cost about half what they do now. The bedrock gravels have con-
siderable thickness, but if they are sufficiently porous to permit of circula-
tion of water through them it is probable that the gold in them would be
concentrated near the bedrock, for it would tend to work down through the
gravels. The gravels, judging by the samples said to have been obtained
from the underground workings and from the descriptions of them in the
managers’ reports, are evidently glacial gravels or “cobble-stone wash”
(as they are sometimes described by the miners) and differ from the “flat
wash” in which the rich pay-streaks in the district are usually found. The
fact that the bedrock gradient of the lower part of Nelson creek from where
it dips off into the valley of Slough creek down to where it joins the deep
channel of Slough creek, is much steeper than in the part higher up, shows
that the bedrock valley of Slough creek was probably deepened by glacial
ice erosion. If there had been no ice erosion of Slough Creek valley Nelson
creek would have been graded to it and would have had a steeper slope in
its upper part than in its lower part, unless a hard rock ridge, of the presence
of which there is no evidence, caused rapids or falls in the lower part.
Streams, normally, have steeper gradients in their upper parts than in their
lower parts because the volume of water is less in the upper parts and re-
quires a steeper slope for its flow. It is, therefore, improbable that pre-

lacial gravels occur in the bottom of Slough Creek valley. The gravels
that occur may be either glacial gravels formed by streams issuing from ice
tongues that lay in the upper parts of the valley or gravels formed by
stream erosion of glacial deposits and partly of the bedrock. They are