34 
TIN DEPOSITS OF THE YORK REGION, ALASKA. 
[No. 229. 
introduced between the fourth and fifth boxes from the upper end 
(see fig. 4). Ordinary patterns of Pole and Hungarian riffles were 
used, except that they were made of 2i by li inch material, which is 
larger and heavier than that ordinarily used in sluicing for gold. 
About 100 miner's inches of water constituted a sluice head for this 
apparatus. It is reported that the concentrates obtained averaged 
about 40 pounds per day to the shovel. The concentrates from the 
sluice boxes were further concentrated Iry hand by panning in a box 
5 feet long by 3 feet wide and 8 inches deep, into which water flowed 
Y-s-A W- 
Fig. 5.— Box used in washing stream tin concentrates. 
through a canvas hose and flowed out over an apron 4 feet long in a 
stream about three-quarters of an inch deep, as shown in tig. 5. The 
concentrated gravel was gradually worked up over the edge of the pan, 
which was kept just submerged at the upper end of the apron, where 
the stream of water carried away the lighter portion, while the heavier 
particles sank in the box. It is reported that concentrates treated in 
this way averaged about 50 per cent tin. The larger pieces of foreign 
matter were picked out by hand. The impurities in the concentrates 
are mainly hematite, magnetite, quartz, and slate. 
Later in the season some sluicing 1 for tin ore was done at several 
