152 GRAVEL AND PLACER MINING IN ALASKA. [bull. 263. 
sponding to approximately 10 per cent of the head under which the 
water acts. Many elevators have been used, and they all act on the 
same principle. One of the necessities is the constant admission of air 
with the tailings, which, by being compressed, aids in the elevating- 
process. Those elevators are considered best which admit air most 
freely . 
An exceedingly simple form of hydraulic elevator — the so-called 
"open" elevator — is in use in southern Oregon. The gravel is piped 
directly into an inclined box 8 by 30 feet in dimensions, which has a 
false bottom of punched iron plates. All the fines run back on the 
plank floor of the box to the undercurrent, the oversize falling to the 
tailings pile at the raised end of the box. The contrivance is a make- 
shift, but is said to be successfully used in the flat stream beds of 
southern Oregon. 
A hydraulic elevator will sink a pit in a flat piece of ground con- 
taining no large stones. In starting new work on placer ground it is, 
in fact, the practice to sink the pit with the elevator. The portion of 
the hydraulic elevator shown in PI. XXVI, A, is in position in the 
bottom of a pit 40 feet deep, on Glacier Creek, Seward Peninsula. 
This pit, which is 90 by 60 feet in dimensions, was sunk in ten days 
by a 7-inch elevator, smaller than the one shown in the picture, using 
325 miner's inches of water at 360 feet head. At the claim next higher 
up the creek a similar elevator was in use, and a description of its 
operation will be of interest. Seven hundred and sixty miner's inches, 
under 330 feet pressure, were used in the operations. The water is 
afforded by the Miocene ditch, described on pages 123-126. The grade 
of Glacier Creek does not exceed 50 feet to the mile in its lower por- 
tion, where this property is worked. The gravel deposit, which is 
wide and 20 feet in depth to bed rock (see PL XXVI, B), can not be 
worked by the hydraulic method on account of the impossibility of 
disposing of the tailings. Therefore a long cut is ground-sluiced off 
to the depth of 6 or 7 feet below the surface. The elevator sump, 
which must be about 5 by 5 feet and 10 feet into the bed rock, is sunk 
in the bottom of the large pit. The elevator, which, with the head 
above given, lifts 36 feet, is set in position. For this ground a No. 1 
elevator, having a 10-inch throat and using 4^-inch nozzle, is employed. 
The hydraulic elevator, like the one shown in the photograph, is by 
no means simple. It consists of 15 large parts, some of them very 
heavy, and a number of rods, bolts, bands, and wooden staves. The 
cost of the one shown is approximately $750 in San Francisco, and the 
weight is 2,000 pounds. A pipe is led from the supply pipe to feed 
the nozzle of the elevator. It is connected to this by means of the 
ball joint. This joint, shown in the photograph, is exceedingly con- 
venient, as it allows the pipe to enter the pit from one of several direc- 
tions. Where the upcast pipe joins the top casting of the elevator it 
