■ 



400 



SUPPLEMENTARY INVESTIGATIONS IN THE GRAVEL REGION. 



drifting was going on. A considerable quantity of white quartz pebbles was to be seen, and there 

 were frequent boulders as large as five or six feet in diameter of an easily cleavable slate. In 

 general appearance the gravel resembled that seen in corresponding positions in the open mines, 

 and it is reported to be very rich. I have not had at my command any data upon which to base 

 an estimate of yield per cubic yard. 



A small deposit of clay with, a few rolled gravel pebbles on the line of the Irwin ditch, a few 

 rods from the Derbec Shaft, was pointed out to me by Mr. Perkins. The deposit is insignificant 

 in extent, and it is worthy of notice principally on account of its altitude, which I made to be 

 only seventy-two feet less than that of the mouth of the Derbec Shaft, or nearly one hundred feet 

 higher than the base of the volcanic stratum. The pebbles at this point were probably picked up 

 by the flowing mud at some higher elevation, and remained permanently enclosed in the volcanic 

 stratum until brought to view by the di 



The Watt Shaft is on Bloody Run, at a point about a mile from Woolsey Elat in a southerly 

 direction, and between half a mile and a mile easterly from where bed-rock first appears in the bed 

 of the creek. At the time of my visit there was no one to be seen at the shaft except the watch- 

 man in charge of the property. Active work has been suspended for a considerable time. I could 

 not go underground at this shaft, and can only give such data as I was able to get by inquiry and 

 conversation. The shaft is said to be 414 feet deep, the first 200 feet being in the volcanic stratum, 

 and the remainder in alternating beds of sand and pipe-clay of varying thicknesses. From the 

 bottom of the shaft a drift was run in a direction a little south of east for a distance of 1,300 feet. 



gging of the ditch. 



Two winzes were sunk from this drift to bed-rock, each one through fifty feet of gravel. The 



gravel, however, was not rich enough to pay for drifting. My observation with the small aneroid 



barometer makes the altitude of the mouth of the shaft to be 4,262 feet. Deducting from this 



the depth of the shaft and the winze, and allowing two feet for rise in the drift, we have 3,800 



feet as the altitude of deep bed-rock at this point. From these figures it appears that the fall of 



bed-rock between the Watt Shaft and the Derbec Shaft is 447 feet. The distance between the 



two points is nearly three miles, and the grade, if uniform, would be not far from 150 feet to the 

 mile. 



1 he exposed gravel deposits nearest to the Watt Shaft are on the opposite side of the ridge 

 which lies between Bloody Run and the Middle Yuba, and are found on four projecting spurs 

 leading down from the main ridge, and separated from each other by deep, canon-like ravines. 

 These places are known as Woolsey Flat, Moore's Flat, Orleans Flat, and Snow Point. I could 

 not learn that the ravines in this neighborhood have any well-recognized names, but the one 

 between Woolsey and Moore's Flat is sometimes called Blue Rank Ravine, the one between 

 Moore's and Orleans Flats is known as Orleans Ravine, that above Orleans Flat as New York 

 Ravine, and that above Snow Point as Golconda Ravine. The gravel at all these points is entirely 

 free from lava capping except at Woolsey Flat. At this last-named point the old channel must 

 have been deflected to the south, for the gravel at the present clay can be seen to pass directly 

 under the lava, and there is no high gravel now to be seen on any of the spurs of the Middle Yuba, 

 slope, below Woolsey Flat, until Badger Hill is reached. 



I took observations to determine the grade of the bed-rock at three points : one near the base of 

 the bank of the Boston Mine at Woolsey Flat ; a second at the most easterly end of the Moore's 

 Flat diggings, opposite Orleans Flat; and a third near the bank of the Shanghai Mine, at Snow 

 Point. The altitude of the bed-rock at Woolsey Flat I found to be 3,890 feet, or ninety feet 

 higher than that of the deepest bed-rock reached at the Watt Shaft, about a mile distant. The 

 altitudes of the bed-rock at Moore's Flat and at Snow Point were 4,019 and 4,211 feet respectively. 

 The precise distances of these points from each other, or from W T oolsey Flat, cannot be given, but 

 it will not be far from correct to say that Moore's Flat is a mile and a quarter above the Boston 

 mine, and that Snow Point is a mile and three quarters above Moore's. From these figures it will 

 be seen that there is a very regular grade of about one hundred feet to the mile between Snow 

 Point and the Watt Shaft. As Snow Point is the highest point on this ridge at which gravel is found 



