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SUPPLEMENTARY INVESTIGATIONS IN THE GRAVEL REGION. 



bluish in shade, though not cemented. There are also some large smooth boulders, up to six or 

 eight feet in diameter. These boulders are usually of slate rock, with occasionally one of granite. 



The altitude of the mouth of Mount Zion tunnel I made to be 4,297 feet, which is 625 feet less 

 than the altitude of the ridge at the junction of Mount Zion and Eureka roads. Adding seventy- 

 six feet for the rise in the tunnel and in the incline, we get 4,373 feet for the altitude of the gravel 

 on the rim of the supposed channel. This point is 162 feet higher than the bed-rock at Snow Point, 

 distant not far from two miles. The depth of the central bed-rock, if any such exists, is not 

 known. Prior to the running of the present tunnel there was an older one run, seventy feet higher, 

 and on about the same grade, which reached the gravel, and from which unsuccessful efforts were 

 made to reach bed-rock by sinking through the gravel. The reason of the failure was the accumu- 

 lation of water. 



The presence of this gravel deposit at Mount Zion lends some support to the belief of Mr. 

 Blaekwell and others, that a high channel crosses the ridge near or above Snow Point ; but I am 

 more inclined to the opinion that such deposits as that at Mount Zion, if they represent old 

 channels at all, are in the places of former tributary streams, — like the supposed tributary by way 

 of Relief Hill and the Derbec Shaft, for example. Whether this supposition is true or not can be 

 easily settled, for the Mount Zion gravel, by pushing the tunnel forward a few hundred feet farther, 

 and tracing the course of the deep channel under the most favorable conditions. That such an ex- 

 tension of the tunnel has not been made before this time excites the suspicion that either capital 

 or confidence has been lacking. 



The volcanic capping of the ridge, which, as has been said, extends in an unbroken line from 

 Columbia Hill, reaches a culminating point, at an altitude of about 5,100 feet, a short distance 

 above Mount Zion and Snow Point. Between this point and Eureka there is a gap in the ridge 

 where the old lava-flow has been broken across by the canons at the headwaters of Poorman's 

 Creek. The Hue of junction between lava and bed-rock is to be seen on the road about half a 

 mile to the southwest of Shand's Ranch. The bed-rock here is slate. About a quarter of a mile 

 west of the town of Eureka, or Graniteville (as the post-office is called), the bed-rock changes from 

 slate to granite. 



Shand's Ranch is on a narrow ridge or backbone, which is the divide between Poorman's Creek 

 and a nameless ravine emptying into the Middle Yuba. The altitude of this point is 4,627 feet. 

 The three main ditches which bring the water from the lakes and reservoirs above Eureka here 

 approach each other very closely, and. run within a few feet of each other for a considerable dis- 

 tance. There are some indications of the presence of quartz gravel on this narrow ridge. One 

 tunnel has been driven in from the Yuba side, about seventy-five feet below the road, and some 

 gravel was found, though not in paying quantities. There is no reason to believe that this gravel 

 is anything more than a small local deposit. If it were a remnant of an old continuous channel, 

 we should expect to find accumulations of quartz and gold in the bed of Poorman's Creek. Such 

 accumulations, I was told, have not been found. 







E. Above Eureka. 



The portion of the ridge which lies above Eureka I did not have time to examine in detail. My 

 observations were confined to parts of two days. By the kindness of Mr. Perkins I was allowed 

 to accompany a load of supplies which was to be sent to the Bowman dam. Leaving Malakoff 

 in the morning, we reached Eureka by the middle of the afternoon and the dam about six in the 



The next day we left the dam about eleven o'clock, in time for me to reach Moore's 



evening. 



Elat before night. 



The bed-rock above Eureka is all granite. The higher ridges are capped with volcanic material, 

 similar in appearance to that seen lower down on the divide between the Yubas, or on the Wash- 

 ington Ridge, to the south of the South Yuba. To the northeast of the town, and a quarter of a 

 mile distant, the lava capping sets in again, as a so-called Bald Mountain ; and this must be 

 regarded as the extension of the same stratum, which, as we have seen, was cut off by the waters 



