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166 



THE AUEIFEEOUS GRAVELS OF THE SIERRA. NEVADA. 



The chief point decided by these measurements on Pine Hill is that the slate rock is altogether 

 too high for the deep channel to have found its way through here. The details of the form of the 

 bed-rotk on the hill itself cannot be known with certainty until further explorations have been 

 made, but this is a matter of only secondary importance so far as the deep gravel is concerned. 

 The key to the solution of the gravel question is to be sought on the lowest, not on the highest 

 bed-rock. It is possible that a channel once flowed in at one side of the present Pine Hill and 

 out at the other, so that the well-defined rim of a large bend in the channel may some time be 

 brought to light'; but I hardly think so. I prefer to adhere to the theory of the filling up of the 



lateral ravines. t 



To the northeast of the Pine Hill gravel, and across a ravine cut in bed-rock, comes the fre- 

 quently mentioned Waloupa. Here there is a considerable exposure of bed-rock. The general 

 course of the long axis of the diggings, across the spur between the two ravines which unite below 

 to make Birdseye Canon, is north and south. . The point where my observation was taken was at 

 the north end of the diggings, directly opposite Niece and West's. The altitude I made to be 

 2 590 feet. Two hundred feet farther to the south there was a place in the bed-rock at least ten 

 feet deeper than where I measured ; but the rock rose again on the opposite side, so that the deep 

 place was probably only a hole. On the east side of the claim the gravel is nearly all removed, 

 and on the west there is a bank of about thirty-five or forty feet in height. At the bottom there 

 is a blue gravel for ten or fifteen feet in thickness, while the upper twenty-five feet, more or less, 

 is made up of layers of red gravel alternating with red or gray sand. This arrangement of the 

 8trata — a substratum of blue gravel covered with red — corresponds in its main feature with what 

 is seen at Niece and West's on the opposite side of the canon, and points unmistakably to the for- 

 mer connection of the two places before the wearing away of the canon between. Above Waloupa 

 there is gravel on the ridge to the north and northwest for several hundred feet, and there are 

 several small mines or openings where work has been commenced ; but there are none at a higher 

 level than the top of the high bank on the opposite side of the ravine, and slate is struck again 

 before we reach the main divide along which the road from You Bet to Colfax and Grass Valley 



The bed-rock at Waloupa, it will be observed, is the lowest that has yet been found any- 

 where throughout this whole gravel district. 



Across the canon from Waloupa in a northeasterly direction is the mine of Messrs. Niece and 

 West, where a great deal of bed-rock has been exposed. Here, as at Waloupa, the bottom of the 

 gravel is blue. The thickness of the deposit, however, is greater. The blue gravel is so firmly 

 cemented together that it is more profitable to run powder drifts and loosen large quantities at a 

 time, than to try to cut it away by the force of the hydraulic stream alone. The upper strata are 



lighter in color and easier to work. 



The deepest part of the centre of the old channel as nearly as could be made out, was selected 

 as the point whose altitude was to be determined. The barometer hung at one corner of the old 

 mill, which is built upon the bed-rock, and indicated an altitude of 2,617 feet, a result which 

 agrees well with what was shown by the hand-level from Waloupa. 

 °To the north of Niece and West's there is a large gravel claim belonging principally, or entirely, 

 to Mr. Williams, but as only the upper gravel has been removed and no bed-rock has been struck 

 in the deep part of the channel, no observation was taken for altitude. 



The next important points, where deep bed-rock is to be seen, are in a northeasterly direction, 

 and on the opposite side of the hill from Niece and West's. Following up the line of Wilcox Ra- 

 vine, to the east of the Little York and You Bet road, there is bed-rock seen at Heydliff's ground, 

 at Brown's, and at Mallory's. There has been considerable drifting done under these banks, and 

 there cannot be much, if any, doubt that the deepest parts of the bed-rock have been cleaned off'. 

 There is not much rock to be seen without entering the drifts, however. Observations were taken 

 at the mouth of the tunnel at Heydliff's and at the bottom of the old incline at Mallory's. Be- 

 tween these two points lies Brown's Mine, where it was not convenient to take any observation. 

 Our results agree very well with those of the spirit-level surveys in giving a fall of about twenty 



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