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 quart 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 simple appliance, which is automatic and requires little attention, will sometimes arrest 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, etc.

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 indiarubber or soft pine wood.

When crushing rich ore, and you want to get nearly all the gold off your plates, the scraper 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.”

Where base metals are present in the lode stuff frequent retortings of the mercury, say not less than once a month, will be found to have a good effect in keeping it pure and active.  For this purpose, and in order to prevent stoppage of the machinery, a double quantity is necessary, so that half may be used alternately.  Less care is required in retorting the mercury than in treating the amalgam, as the object in the one case is more to cleanse the metal of impurities than to save gold, which will for the most part have been extracted by squeezing through the chamois leather or calico.  A good strong heat may therefore at once be applied to the retort and continued, the effect being to oxidise the arsenic, antimony, lead, etc., which, in the form of oxides, will not again amalgamate with the mercury, but will either lie on its surface under the water, into which the nozzle of the retort is inserted, or will float away on the surface of the water.  I have also found that covering the top of the mercury with a few inches of broken charcoal when retorting has an excellent purifying effect.

In retorting amalgam, much care and attention is required.

First, never fill the retort too full, give plenty of room for expansion; for, when the heat is applied, the amalgam will rise like dough in an oven, and may be forced into the discharge pipe, the consequence being a loss of amalgam or the possible bursting of the retort.  Next, be careful in applying the heat, which should be done gradually, commencing at the top.  This is essential to prevent waste and to turn out a good-looking cake of gold, which all battery managers like to do, even if they purpose smelting into bars.