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516 DISTRIBUTION OF THE GOLD IN THE GRAVEL. , 
east, this would be an evidence of the existence of that ridge in the gravel period, and that it 
acted then as a barrier which the streams could not cross, but were obliged to pass around. 
It is the general fact throughout the gravel region, —to which there are indeed occasional 
though rare exceptions, — that in any given bank the richest portion of the gravel, as well as that 
containing the coarsest gold, is that which lies at the bottom, immediately upon the surface of the 
bed-rock. In order to account for this fact, the idea has been advanced that it was not originally 
so, but that the gold was distributed through the upper as well as the lower portions of the 
bank with much greater approach to uniformity, so that there was at first but little difference 
in richness between the gravel immediately upon the surface of the bed-rock and that higher 
up towards the top of the bank. Afterwards, however, as is supposed, the coarser particles and 
lumps of gold, by virtue of their high specifie gravity (and apparently also by virtue of some 
further and mysterious faculty which they must also in that case have possessed, of pushing aside 
the sand and pebbles ina firm and compact bank), gradually settled down through the under- 
lying gravel until at last they reached the surface of the bed-rock, and so became concentrated 
there. Now this explanation appears very unsatisfactory to me, because, in the first place, I do 
not believe that, high as is the specific gravity of gold, it is sufficient to cause particles and pellets 
of it, no larger than those which are commonly found in tunnel and hydraulic mining, to displace 
the firm gravel beneath them, and actually thus sink through it, however slowly, to the rock ; and 
in the second place, because I further notice that it is also a general rule, wherever very large 
boulders occur in a bank of gravel, that these, too, are at the bottom, either immediately upon or 
very near the surface of the rock. It is very rare indeed to find very large boulders at any great 
height above the bed-rock in banks of metamorphic gravel; and for these boulders, at least, the 
sinkage theory will not do. I do not deny, of course, that earthquake shocks, or anything else 
which severely jarred the ground, might cause large lumps of gold, if such were imbedded in the 
gravel, to settle a little. Nevertheless, I do not believe that any great portion of the gold has 
sunk very far through the mass of gravel in this way or in any other. I can see but two plausible 
methods of accounting for the almost universal fact. The first of these is by supposing that the 
earliest gravel streams flowed at first for a long period of time over the naked bed-rock, deriving 
large quantities of auriferous débris from somewhere, though without excavating their own channels 
to any considerable depth in the rock, and at the same time without accumulating any consider- 
able quantity of gravel in their channels, the rocky débris, wherever it came from, being thor- 
oughly disintegrated or ground up, and carried on by the streams, while the gold which it contained 
was gradually concentrated in their beds, — the era of accumulation only commencing later in the 
history. This supposition, if admissible, might account perhaps for the bottom gravel being the 
richest in gold ; but there are serious difficulties in the hypothesis itself, aside from the fact that 
it does not account in the least for the general absence of all large boulders from the upper por- 
tions of the deeper banks of metamorphic gravel, while they are plenty enough in the same banks 
immediately upon and near the bed-rock. 
A much more plausible, and I am strongly inclined to think the true, explanation of both these 
facts lies in the hypothesis (if, indeed, it be not something better already than a hypothesis) that, 
as a general rule, neither the coarsest gold nor the largest boulders were ever transported very far 
from the spots whence they were originally derived. It is easy to see how, if this were true, the 
two facts named would be necessary consequences of it. For as the gravel at any particular local- 
ity, or in any particular channel increased in depth, so also would it increase in lateral extent, 
and more especially would the length of channel-bed already covered rapidly increase, and thus 
would increase with exactly equal rapidity the distance through which any additional material 
must roll over the surface of the gravel already accumulated before it could reach a position over 
the already deeply buried spots. 
But there is another point in connection with the gold of the ancient gravel, which is far more 
difficult to explain. It is the uniform testimony of mining men throughout the gravel region that, 
as a general rule, the coarser the gold from the gravel banks, the less is its value per ounce. Now, 
