Page:Popular Science Monthly Volume 61.djvu/241

Rh the limited area intersected by the auriferous creeks which radiate from the Dome.

Some of the gold adheres to quartz, which exactly resembles that of the veins in the adjoining schists; and it is fairly certain that the metal came from quartz veins in the Klondike schists.

On the other hand it is certainly most remarkable that so little auriferous quartz has been found; at the time of my visit hundreds of quartz claims had been staked, but very few had been shown to contain any gold whatever; neither do the quartz boulders of the White Channel appear to be auriferous, or even mineralized. And yet it can hardly be doubted that where the valley gravels are rich in gold above their intersection with the White Channel the metal must have been derived from quartz veins in the schists.

In one instance I found direct evidence bearing on this question. In Victoria Gulch, a streamlet which descends into El Dorado Creek on its left bank high up the valley, have been found small flat crystals of gold of peculiar shape known as 'spinel twins.' In visiting a quartz vein at the head of Victoria Gulch (near the summit of the divide between El Dorado and Bonanza creeks), which had been lately opened and found to contain visible gold, I noticed precisely similar crystals. Here, at any rate, there can be little doubt that the gold in the creek has been derived from quartz veins in the schist.

No crushing has yet been carried on in Klondike; the gold has been entirely won by washing the gravels.

The chief difficulties of Klondike mining are due to the permanently frozen ground, which has led to certain peculiarities in the methods adopted. Every yard of gravel which is sluiced must first be thawed, either by artificial means or by exposing it to the rays of the summer sun after stripping off the overlying muck; for it is impossible to work the frozen ground with pick or spade, or even with dynamite.

Until recently shafts were sunk or tunnels were driven by laboriously thawing the ground with hot stones or wood fires; and I saw both methods in operation during my visit. The latter process—firesetting, as it is called—is, in fact, quite frequent. A layer of dry wood is piled up against the face of the gravel, blanketed behind by a layer of green wood, ignited, and allowed to burn itself out; twelve hours of burning would thaw out little more than one foot in depth; and the process is then repeated.

Upon the larger properties this method has been entirely replaced by 'steam-thawing.' In this four-to six-foot lengths of iron piping, tipped with steel nozzles, are inserted into the gravel, and steam is forced through them at a pressure of about 120 pounds. These pipes are known as 'points'; one point is inserted to about each square yard, and is driven in gradually by taps from a hammer; each point will thaw