200 GRAVEL AND PLACER MINING IN ALASKA. [bull. 263. 
expanded-metal form of riffle table, which has given good satisfaction. 
The f-nes were, after passing out of the 96 feet of sluice boxes follow- 
ing the tables, elevated by a steam scraper to a pile 200 feet distant 
and 15 feet high. The expense of installation of such a plant will be 
not less than $5,000, and will more likely be $10,000 in any part of the 
interior of Alaska. 
In arranging a number of gold-saving tables to receive the discharge 
from a screen, great care should be taken to distribute the material 
equally to these tables, so that the duty of each may be the same. 
This in the best Oroville practice is done by leading a small sluice 
trough from the main receiving sluice beneath the screen to each of 
the tables. In case of a second sizing, as in the Atlin dredge described 
below, the distribution is necessarily accomplished by a series of griz- 
zlies in the main sluice. If small ducts or troughs are used, they 
should be provided with gates, the whole made of wood, like those 
used for distributing the pulp to the tables in concentrating mills. 
The attempt to distribute the fines directly from the trommel by means 
of iron gates is considered less satisfactory. 
Riffles for the saving of fine gold in sluices are of many kinds and 
are of very ancient origin. Humboldt (Asie Centrale) refers to the 
Scale of feet 
Fig. 45.— Pole riffle fitted with knives for breaking clay. 
method in use of working the placers of Colchis — that of employing 
wool in the sluices — as a possible explanation of the legend of the 
"Golden Fleece." It was in fact known that the kings of Imeret in 
the eighteenth century used wool for collecting gold in Tskinitskali 
and Abacha rivers in the Caucasus, while Turkish gypsies use goatskin 
for gold saving on Belichta River. 
The pole riffle made of saplings, with or without strap iron nailed 
to the top, has long been in favor in small placer operations in the 
United States, and is to-day employed in the primitive shoveling-in 
operations throughout the northern territory. An improvement on 
this riffle, simply made, aiding in the disintegration of clay, was seen 
by Mr. Frank L. Hess in the Rampart district of Alaska, and a sketch 
furnished by him is shown in fig. 45. Small squares of sheet iron 
one-sixteenth inch by 2 by 2 inches are driven cornerwise into the 
poles. 
A development from the wooden pole riffle is the iron or steel rail, 
laid longitudinally in the sluice box. One type of rail riffle used in 
Seward Peninsula is shown in fig. 32. It will be noted that the T 
lies with its horizontal extension uppermost, that the rails are joined 
