[Fig. 672 enlarged] (128 kB)

This figure represents the general ground plan of a stamping and washing mill. The stamps F are composed of two batteries similar to [fig. 670.] The ore passes in succession under three pestles of cast iron, each of which is heavier the nearer it is to the sieve through which the sand or pounded matter escapes.

In the upper part of the figure we see issuing from the stamps, two conduits destined to receive the water and the metalliferous sand with which it is loaded. The first, marked F, S, w, is used only when a certain quality of ore is stamped, richer in metal than is usually treated by means of the second conduit, the first being closed. The second conduit, or that employed for ordinary manipulation when the other is shut, is indicated by F, 0·7, B; then by 0·58 and 0·29. These numbers express the depth of the corresponding portions of this conduit. From F to B, the conduit or water-course is divided into three portions much shallower, called the rich conduit, the middle conduit, and the inferior. Beyond the basin B, the conduit takes the name of labyrinth. There the muddy sediments of ore are deposited; being the finer the further they are from the stamps F. Darts indicate the direction of the stream in the labyrinth. On the German chests, placed at 3, the sand derived from the rich and middle conduits is treated, in order to obtain three distinct qualities of schlich, as already mentioned. P is a cloth-covered table, for treating the deposit of the German chests at 3. M N are two sweep tables (à balai), for treating the ore collected in the lower conduit, which precedes the midmost of the three German chests. Upon the three similar tables R T V, are treated in like manner the muddy deposits of the labyrinth, which forms suite to three parallel German chests situated at 3, not shown for want of room in the figure, but connected in three rectangular zigzags with each other, as well as by a transverse branch to the points 0·7 and P. At the upper part of these five sweep tables, the materials which are to undergo washing are agitated in two boxes O O, by small paddle-wheels.

We shall now describe the percussion-tables used in the Hartz, for treating the sand of ore obtained from the conduits represented above.