

438 



SUPPLEMENTARY INVESTIGATIONS IN THE GRAVEL REGION. 



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little drifting done in this mine. I have not the full data for a detailed history of this exploration, 

 and in the following description the distances given are only approximate. For the first 500 feet 

 the tunnel was in gravel. Then there came 150 feet of clay resting upon gravel, followed by 150 

 feet of clay resting upon bed-rock. Beyond the clay the tunnel was in a soft slate for 300 feet, 

 and then in pay-gravel, 325 feet farther, to the air-shaft. The shaft is 1,425 feet from the mouth 

 of the tunnel. The strata met with in raising the shaft were, — twenty feet of gravel, forty feet of 

 pipe-clay, and two hundred feet of volcanic cement. Beyond the air-shaft the tunnel was driven 

 for 2,000 feet in bod-rock, with gravel from fifteen to twenty feet over-head. A coarse pay-gravel 

 was then followed for 300 feet, to a so-called " lava cement," containing some coarse and some 

 fine boulders, with about two feet of quartz gravel next the bed-rock. At the present face of the 

 tunnel there is a thin gravelly cement on the bed-rock, covered with a sandy clay containing good 

 impressions of leaves. The gold found is rather fine, and black sand is said to be plentiful. These 

 explorations have so far failed to confirm, the belief that the main channel lies to the west of that 

 in the Raid Mountain mine. At present I am inclined to the belief that the gravel found in the 

 North Fork mine, as well as that reported from other places, lying to the west of Alleghany and 

 Chips's Flat, which I was not able to examine in person, does not belong to any continuous and 

 independent channel, but was in some way once connected with the more easterly deposits. 



Between Forest City and City of Six the gravel is nowhere exposed to view at the surface of 

 the ground. At Rock Creek there used to be a mine worked by means of an incline, which is no 

 longer accessible. About a quarter of a mile below the old incline Mr. William Irelan is driving 

 a new tunnel, known as the Ruby Tunnel. The tunnel starts in a soft and clayey slate bed-rock, 

 which requires but little blasting, and follows a southeasterly course for about 450 feet, when the 

 course is changed to the east, and a branch is started to the northeast. Gravel has been found 

 about twenty feet above the main tunnel, and near the roof of the branch. Between these points 

 the gravel is continuous, and the bed-rock has a pitch to the east or northeast. My barometric 

 measurements cannot, of course, be relied upon to determine with accuracy small differences of 

 level, or to settle the question, whether or not it is possible for a gravel connection to exist between 

 Rock Creek and the Bald Mountain mine. The altitude of the mouth of the Ruby Tunnel I made 

 to be 4,800 feet, and Mr. Irelan's estimate is, that the gravel in the Ruby Tunnel lies upon a side 

 bench from seventy-five to one hundred feet above the deep channel, the level of which is known 

 to be below that of the bed of the present Rock Creek. Taking into account the grade of the 

 tunnel, and adopting the lower of Mr. Irelan's estimates, it may be said that the deep channel lias 

 an altitude of 4,750 feet. The mouth of the Bald Mountain tunnel I made to be 4,489 feet above 

 sea-level. If the rise in the tunnel is uniformly four feet to the hundred as far as the shaft, 1,800 

 feet from the mouth of the tunnel, the altitude at the bottom of the shaft is 4,561 feet. Between 

 this point and the bottom of the Rock Creek incline there is a difference of level of 226 feet, accord- 

 ing to the survey made by Mr. I. G. Jones, county surveyor of Sierra County. If these data are 

 correct, the altitude of the Rock Creek channel is 4,787 feet, thirty-seven feet higher than I made 

 it to be with the barometer. The distance between the shaft and the incline is probably between 

 a mile and a half and two miles, which, supposing the grade of the Bald Mountain channel to con- 

 tinue to be as much as four feet to the hundred, would require from one to two hundred feet more 

 difference of altitude between the places than really exists. The grade of the Bald Mountain 

 channel, however, grows less as the tunnel increases in length, and I see no reason why there may 

 not be an uninterrupted stratum of gravel between the present face of the Bald Mountain tunnel 

 and Rock Creek. Against this hypothesis it is urged that the Rock Creek gravel lies in a narrow 

 channel, only sixty feet in width, and that the gold of Rock Creek is different in character from 

 that of Bald Mountain. I brought with me from Ruby Tunnel a few pieces of gold, given me by 

 Mr. Irelan, which have been examined by Mr. Wadsworth, who says of them : " Tin's gold shows 

 the impress of the vein-stone, and while the thinner parts have been bent over and in upon the 

 main mass, the grains as a whole seem to have suffered more from wear than from the direct 

 pounding of the pebbles upon them. This came from a white clayey or fine sandy bed. The 



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