

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 



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up towards the top of the bank. Afterwards, however, as is supposed, the coarser particles and 

 lumps of gold, by virtue of their high specific 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 in a 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 bouklers, 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 debris 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 debris, 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, 





