WASHING FOR GOLD AND PLATINUM.--This operation, called “panning,” is the oldest and simplest method of extracting the precious metals. At the present time, it furnishes to Russia nearly all the gold produced in that empire. It is based on the principle that substances of different weights may be separated by means of water,--the heaviest going to the bottom first. To examine the bank or bed of a river, suspected to contain gold, fill a milk-pan with the sands and carry it to a tub or pool of quiet water. Dip it under, stirring the mass with one hand or a stick. Then pour off the muddy water, fill with fresh water stirring again, and again pour off the light sand, clay, etc. Scales of gold will sink fast; mica flakes will take their time. Repeat this process till all the fine particles are washed off; then allow just enough water to enter the pan as will cover the sand. By shaking the pan and gradually lowering the side by which it is held, the light sand will flow off, leaving in the corner a heap of coarse sand. Put in a small quantity of water and turn the pan around so as to create a gentle current, when the precious metal, if there be any, can be easily detected,--the gold by its bright lustre, the platinum by its lead color, and both by their malleability. Particles of gold are of uniform color and are either flat or rounded; while other yellow grains are angular. Holding the pan in the sunshine, secure any glittering glassy crystals, and test them for diamonds or rock-crystals. A magnet will remove any particles of magnetic iron-ore. ASSAY OF GOLD ORE.--Gold may be found in quartz rock, in iron and copper pyrites, and in silver ores. To ascertain if any gold is present in quartz, reduce the rock to powder and sift it. A certain quantity, say half a peck, is then washed as above described, till a manageable quantity of sand is left. If there is any show of gold, dry the mass and put it in a bowl or glass dish, and add an ounce of quicksilver, stirring the mixture well with a wooden rod. The quicksilver, which will unite with every particle of gold which may be there, is then poured off into a soft leather (chamois) bag. This is squeezed to remove superfluous quicksilver, and a pasty amalgam is left, which is put into an iron vessel and heated red hot. The yellow powder remaining is mixed with saltpetre and melted, when a button of pure gold will be found in the crucible. Quartz ores should yield $6 to the ton in order to pay. To test pyrites for gold, reduce a given quantity to powder and wash as before; then roast the residue at a red heat. Upon cooling, add quicksilver and treat as just described. Pyrites should yield $1 of gold to the bushel of ore to be profitable.