PrRIN'GTON.l 
HYDRAULIC MINING. 
149 
In hydraulic elevator practice as pursued in various parts of Seward 
Peninsula, Alaska, short sluices are in use. I [ere, as elsewhere, a sluice 
is generally set in bed rock on a grade of 1<> inches to 12 feet, or near 
this grade. On Ophir Creek, in the ( ouncil district, Alaska, the prac- 
tice is to use from 10 to 12 boxes of 12 feet length, 24 inches wide and 
LG inches deep, with wooden rail or pole rimes, shod with strap iron. 
This leads to the elevator sump, 10 feet deep. The position of the 
elevator with reference to the sluice below it is shown in PI. XXV, J. 
The tail sluice following the elevator in the case specified is 28 feel 
higher than the head sluice. The tail sluice consists of five 24-foot 
boxes, 4 feet wide, and the practice is to give the first box either no 
grade, or a grade not exceeding 2 inches. The other boxes are graded 
from 2 to 5 inches successively, a 5 inch grade being retained for all 
below the fifth box, if more are added. On Ophir Creek, where there 
are six elevator plants in operation, iron rimes are generally used in 
the discharge sluice. A type of riffle which is used in the head box 
is made of railroad iron, cut in short pieces and set transversely in 
c 
1 1 
1 1 
IT 
IT 
I i 
-- 6ft- 
Scale 
2 feet 
Fig. 32.— Rail riffles used in Seward Peninsula. 
the box, forming a Hungarian riffle. Another kind in much favor 
throughout Seward Peninsula is composed of a set of T rails, in sets of 
4 laid lengthwise (see fig. 32). These are made with a locking attach- 
ment, and are put in the sluice upside down. T angle-iron riffles, 
made in 1-foot square castings, laid in the- sluice so that the slots set 
longitudinally, and with the flat side uppermost, are also very satis- 
factory and durable, and on account of their lightness facilitate, the 
clean-up. 
The proportion of gold caught in the head and tail sluices varies 
according to the practice. At Claim No. 2, below Glacier Creek, the 
gravel is run through 250 feet of iron boxes, only the two lower of 
which, next the elevator sump, contain riffles. These iron boxes are 
10 feet long, 31 inches wide at the top, 27 inches at the bottom, and 8 
inches deep, of a single bent sheet of iron, lapping 2 inches at the ends 
and fastened together with two bolts. The material slides easily 
through the cut in these, which are laid on 6-inch grade to the eleva- 
tor. It is said that 50 per cent of the gold is caught in the last two of 
these, and 50 per cent is caught in the tail sluice after the elevator. 
