fed in small streams of water down the inclined surfaces of sloping
glass, or other smooth shelves set close to and parallel with one
another near the periphery of such a vessel of moving water, the
resultant motions of the heavy and of the light particles
respectively, in passing down these shelves, will be found to be so
different that the good stuff can be caught by a receptacle placed at
one part, while the tailings fall into another receiver which is
differently situated at the place where the lighter grains fall.

The main essential in this particular application of the art of
vanning is simply that the water should move or drift transversely to
lines of ore passing, while held in suspension with water, down a
smooth sloping surface. In dealing with some very light classes of
ore, and especially such as may naturally crush very fine--that is to
say, with a large proportion of impalpable "slimes"--there is a
decided advantage in causing the water to drift sidelong on the smooth
shelf by other means than the motion in a circular tank.

Adopting nearly the form of the "side delivery manner," in which the
moving band is canted to the side and the stuff runs off sideways, the
sloping smooth shelf can be worked for ore separation with merely the
streams of water holding the fine sand in suspension running down at
fixed intervals. A glass covering is placed very close to this surface
on which the streams run; and between the two is driven laterally a
strong current of wind by means of a blast-fan, which causes each
stream of water to drift a little sidewards, carrying with it the
lighter particles, but leaving on its windward side a line of nearly
pure ore. These small runlets can be multiplied, on a shelf measuring
six or eight feet in length, to such an extent that the machine can
put through as much ore as a dozen vanners, consuming only a mere
fraction of the power necessary to drive one machine of the older
type.

Cyanide solution, instead of water, is very advantageously employed
for this kind of operation in the case of extracting gold from crushed
ore. The method is to pump the liquid from the tanks in which it is
stored and to allow it to flow back by way of the vanning apparatus,
thus providing not only for catching the grains of gold by the
concentrating machine, but also for the dissolving of the fine
impalpable gold dust, or natural precipitate, by the action of the
cyanide of potassium.

Upon the use