When the double agitator is used, two riggers will be necessary, as at L and W, and the one at W, which communicates with the large external agitator, is made double the diameter of the smaller one L, which is fixed upon the iron axle H, in order that the small internal agitator may move with double the velocity of the large external one. In every other respect, this machine is the same as the one already described. Fig. 6, is an elevation of a machine, with a double agitator introduced, merely to show how such a machine, oil a small scale, may be moved by hand. I and w are the two riggers of the internal and external agitators, as in the last figure, and motion is communieated to them by the bands m m, which pass round the two riggers v and u, both of the same diameter, and both fixed upon the upright iron shaft xx, which also carries the bevelled wheel y, which is driven by the larger wheel Y, hung upon the main shaft, which also carries a heavy fly wheel zz, and the winch or handle by which the whole is turned.
The timber framing t t, for carrying the said wheel and riggers, is too obvious to need description, and may be varied in form, to suit the convenience of the place in which the machinery is fixed; and when a horse is adopted for machinery of magnitude, it is almost needless to observe, that it must take into, and drive the wheel y, which for this purpose may be fixed higher on its shaft, when the wheel y, with its fly wheel, shaft, and handle, will be unnecessary. In the use of this machine, it is vain to expect to get the ore or other heavy material, separated from the sand, earth, or other material, with which it may be mixed, in a clean and perfect state, by one operation as hereinbefore described, because a considerable portion of sand and earth will inevitably run off with it in the water. The mode proposed by the patentee therefore is, to save all the first portions that run off from the central valve at the first washing, in a tub or other receptacle by themselves; and when a sufficient quantity is thus accumulated, it is to be again put into a machine, which may be smaller for this purpose, and it is to be treated precisely in the same manner as the crude materials in the first instance, when it will be further cleansed and purified; but if not in a sufficiently clean state after this second washing, it must undergo a third, or even fourth, in the same or smaller hand machines, according to the purity required; which by due and attentive care to the directions herein given, and a little practice, may be carried into any extent required.
It is also necessary to observe that the operation of washing and separating ores, or other heavy materials, by the machinery before described, may be effected, (though in a less convenient manner,) without the adoption of either of the bottom central valves, or any valves at all; because such heavy materials, if not permitted to escape by the valves, will accumulate in a heap in the centre of the tub, and will be found upon carefully removing the sand, earth, or matrice from around about it; or another process may be used, such as the apparatus delineated in the subjoined Fig. 7, is adapted for.
In this case a shallow tub is set within a deeper and larger one T, either with or without the blocks l l to raise it above the bottom of the exterior tub; or the inner tub may be fixed in a running stream, or a stream may be made to run continually into and out of it. When the apparatus is arranged in this form, the revolving motion of the agitator F F I I will have the effect of throwing most of the water that is introduced with the ore into the shallow tub, over its edges into the external tub, or into the running stream, (as the case may be,) or into a reservoir; and with it nearly all the sand, earth, or matrice will be thrown over, so as to leave the ore, or other heavy material, in a nearly clean state at the bottom of the tub, particularly if a sufficient quantity of water has been used during the process.
The whole agitator is now to be removed, for taking out the clean ore, and when an accumulation of refuse has taken place in the outer tub, (if such a one be used,) the inner one is to be removed, and the agitator lowered into the other large tub for stirring up the said refuse and water, while it is drawn off by the plug, or spigot and fauset at S; after which such refuse and water are to be again passed through a machine by way of examination, to ascertain if any ore, etc. had passed over with it; and if so, it will be obtained at this second washing. The refuse and water might be led over coarse flannel or cloth, in which the heavy material would deposit itself, if there be any left in the refuse. It may likewise happen in some cases, that the ore, or other heavy substances, cannot be conveniently broken down and reduced to powder, but may contain diamonds, precious stones, lumps, or fragments which would be too large and heavy to be put into motion with the water, as before described; whenever this is the case, the construction of the agitator, shown in Fig. 7, is recommended, which in effect is the same as those already described; but instead of intersecting the arms F F.which carry the stirrers I I I I into the central block of wood already described, a circular kind of funnel or hopper is constructed as shown in section at gggg, of iron, and the spindle revolves into transverse pieces m m within the said hopper; such pieces being placed with their thinnest dimensions upwards, so as to cause as little obstruction as possible.
This hop per is to be fed with ore (previously broken into small pieces), by means of the shoot n n, which may be shook by joggles at r, like a cornmiil, or be fed by any other convenient method. Fig. 7 also shows another form of the agitator: a double set of arms to carry the stirrers, is not essential; all that is necessary is, that it should possess sufficient strength and substance to put the whole of the water and heavy materials mixed therewith, into a sufficiently rapid motion, to produce the conical hollow space similar to k k k, Fig. 3, as before described.