192 



THE AURIFEROUS GRAVELS OF THE SIERRA NEVADA. 



* 



consolidated, 1,400. This makes, in all, for the seven companies following each other in order 

 from the Babb to the Smartsville consolidated inclusive, 9,000 feet, or nearly one and three 

 fourths miles ; so, the total length of a line drawn through the centre of the whole gravel deposit 



would be a little over three miles. 



The width of the channel, or pay gravel, at each company's workings it is not easy to give with 



At Timbuctoo, the Antone Company has worked down to the bed-rock, so as to show a 

 — the old original water-course, as it were — now filled with blue gravel, or blue 





accuracy. 



deep channel 



cement, a material so closely cemented or compacted together as not to be capable of being moved 

 by water without the aid of previous blasting. This lower channel has a width of seventy-five or 

 a hundred feet. But higher up the gravel was deposited over a much greater width, so that the 

 Antone Company's workings were 700 to 800 feet wide ; and in one place, it is said, as much as 

 1,200. At the Babb Company's claim the width of the channel worked is said to vary from fifty 

 to 300 feet. At one point in the Rose's Bar workings the channel was said to be 600 feet wide ; 

 in the Blue Gravel ground the estimated width is from 150 to 300 feet. It is evident that the 

 width of ground which it pays to work is not a fixed quantity, the breadth of the channel varying 

 considerably within short distances. 



The thickness of the gravel at this locality is considerable, but variable. Near the Warren and 

 Antone Company's claims the top of the bank was found by barometric measurement to be 172 

 feet above the bed-rock at the nearest accessible point. The top of the bank in the Antone Com- 

 pany was stated by Mr. McAllis to be 150 feet above the "white cement," — this being a local 

 term for the blue gravel filling the deepest portion of the channel, given probably on account of the 

 preponderance of quartz pebbles in it at that particular place. Eastward of the Antone Company 

 the following data were obtained in reference to the depth of the gravel worked : At the Babb, 

 average height of the bank, to the level of the old river channel, 100 feet, and the old channel 

 itself eighty feet, and here some of the lowest portion of the bed-rock has been exposed by washing. 

 At the Pactolus, a bank of 130 feet in height was worked off before reaching the " old channel" ; 

 a shaft was then sunk ninety-six feet — for the last thirty feet in blue gravel — without striking 

 the bed-rock. The Rose's Bar Company were, in 1870, working off their upper stratum of graved 

 to a depth of from 100 to 130 feet, a deeper tunnel being required to work the remainder, the 

 exact depth to the bed-rock at this point not being known. The Blue Point Company were work- 

 ing a bank of from forty to 120 feet in height; but required a deeper tunnel for washing their 

 deeper gravel. Thus it will be seen that there is in this region a channel of variable width, the 

 upper portion of which in places expands out to as much as 1,200 feet; that ordinarily the higher 

 portion of this channel varies from 300 to 600 feet in width ; that the bottom of the gravel lies 

 within comparatively narrow limits, and that in this "old channel," which is less than a hundred 

 feet wide, the graved is more solidly compacted together than it is in the higher and wider portions 

 of the deposit. The general course and position of the channel will be easily recognized on the 

 map. The thickness of the gravel is in places over 200 feet, and over a large portion of the 

 deposit nearly as much as that. Owing to the great depth of the channel, very long and expen- 

 sive bed-rock tunnels have been required here to reach the bottom of the gravel. That of the Blue 

 Point Company occupied four years in its construction, and cost, it is said, $ 146,000; it is 2,270 

 feet in length. The first tunnel of the Blue Gravel Company was eight years in building, and 

 cost over $ 100,000 ; but does not drain the lower portion of their ground. Another and a deeper 

 one was in progress in 1870, to be 1,500 feet in length and to occupy five years in its construc- 

 tion. 



In the early days of hydraulic mining in this district the sluices were comparatively short, that 

 of the Michigan Claim, for instance, being from 400 to 800 feet in length only, and of course with 

 a higher grade, perhaps as much as ten or eleven inches to the box.* In those earlier days the 



* A " box " is always twelve feet in length ; it is one section, or piece, of the sluice, and by putting 

 more or fewer " boxes n together the sluice is made of any length desired. 



