I have tried a further adaptation of this process when treating ores containing a large percentage of iron oxide, where the bulk of the gold is impalpably fine, and contained in the “gossan.” At the end of the blanket table, or at any point where the crushed stuff last passes before going to the “tailings heap” or “sludge pit,” a “saver” is placed. The saver is a strong box about 15 in. square by 3 ft. high, one side of which is removable, but must fit tight. Nine slots are cut inside at 4 in. apart, and into these are fitted nine square perforated copper plates, having about eighty to a hundred 1/4 in. holes in each; the perforations should not come opposite each other. These plates are to be amalgamated on both sides with mercury, and the top plate “fed” from time to time with mercury, in which a very little sodium has been placed. If acid ores are being treated, zinc should be employed in place of sodium, and to prevent the plates becoming bare, if the stuff is very poor, thick zinc amalgam may be used with good effect; but in that case discontinue the sodium, and occasionally, if required, say once or twice in the day, mix an ounce of sulphuric acid in a half gallon of water and slowly pour it into the launder above the saver. Underneath the “saver” you require a few riffles, or troughs, to catch any waste mercury, but if not overfed there should be no waste. This automatic appliance sometimes arrests a considerable quantity of gold. We now come to the subsidiary processes of battery work, the “cleaning” of plates, and “scaling” same when it is desired to get all the gold off them, the cleaning and retorting of amalgam, and of the mercury, smelting gold, &c. Plates should be tenderly treated, kept as smooth as possible, and when cleaning up after crushing, in your own battery, the amalgam--except, say, at half-yearly intervals--should be removed with a rubber only; the rubber is simply a square of black india-rubber or soft pine wood. [Illustration: FIG. 23. SCRAPER.] When crushing rich ore, and you want to get nearly all the gold off your plates, the scraper (Fig. 23) may be resorted to. This is usually made by the mine blacksmith from an old flat file which is cut in half, the top turned over, beaten out to a sharp blade, and kept sharp by touching it up on the grinding-stone. This, if carefully used, will remove the bulk of the amalgam without injury to the plate. Various methods of “scaling” plates will be found among “Rules of Thumb.”