182 GRAVEL AND PLACER MINING IN ALASKA. [bull. 263. 
merly, and arrangements are such as to allow a better distribution ol 
sluicing water to various parts of the gold-saving areas. Gold-savinc 
surfaces are now generally arranged in a number of drops, and th< 
material impinges upon riffles charged with mercury and is amalga- 
mated by impact. 
Much thought has been recently given to the perfecting of save -alls, 
and a surprisingly large amount of gold, sometimes 10 per cent of all 
saved, is recovered in this way. The design of save-alls in the earlier 
practice was somewhat neglected, but in the general refinement 
of working methods a considerable improvement is being effected. 
A device for keeping under lock and key parts of the gold-saving 
apparatus where the largest proportion of gold is caught has been 
introduced. 
The t roughed belt stacker seems to be generally regarded as supe- 
rior to the bucket stacker (see PI. XXXIV, B) because of greater 
economy of operation and less weight for a given length. Stacker 
belts are a source of large expenditure because of the rapid wear due 
to the insufficient thickness and inferior quality of the material which 
covers the woven part of belt and which gives the belt its wearing 
qualities. 
Nearly all the recently installed stackers have the driving pulley on 
the outboard end, and electric dredges have the driving motor, as 
well, on the outboard end. (See PI. XXXIV, A.) This arrangement 
has eliminated a number of troublesome features. If the stacker isj 
driven by rope or sprocket chain from a motor on the dredge, there 
is much trouble due to wear, slipping, and stretching of ropes and of 
sprocket chains. If the driving pulley is at the inboard end of the 
stacker, the load is pushed uphill on the slack side of the belt, and 
there is much trouble from slipping and stalling. A belt stacker 
driven b}^ the inboard pulley requires more power than one operated 
by the outboard pulley. 
At one time it was generally thought that when coarse gold occurred 
in the material dredged, either the double or single lift type of dredge 
must be used. Stacker dredges are now used and have at the lower 
end of the trommel perforations large enough to pass material up to 
H inches in diameter. This material and water run through a sluice 
where gold is saved and are then deposited in the stacker buckets. 
With such a device under ordinal conditions a troughed belt stacker 
could not be used, as it could not handle the water. Any device that 
would remove water and deposit pebbles on the belt without too many 
complications would allow the use of the belt stacker. (See PI. XXXV, 
A, p. 184.) It would not be expedient to use a double or single lift 
dredge where ground is deep. To effect disposition of tailings while 
operating the double and single lift dredges it is necessary to keep the 
pond nearly full and to use very long digging ladders 
