INCREASE IN THE GOLD PRODUCE OF RUSSIA. -- According to the last intelligence from Siberia, the enterprise of gold washing has extended itself from the eastern side of the Ural Mountains to the Altai, and layers of gold sand have been found to extend along the Chinese frontier over a pace of 80,000 square miles, of which the 200th part in the Ural districts alone furnishes an average of 300 pouds (the poud is 32 2/3lbs.) a year -- equal to 1500,000 of paper roubles.  Professor HOFFMANN has observed, that the masses of granite, hitherto deemed barren, of which this chain of mountains is composed, contain gold.  In order to keep up, in some measure, the price of this metal, Gen CANCRIN has deemed it advisable to raise the tax ten per cent, and see that it will be necessary to claim the crown's right to the fifth part of the produce amounting last year to 400 pouds in Mount Altai.  Should the hopes at present entertained be realized, and no unforeseen events take place, this sudden increase in the quantity of gold will affect the precious metals equal to the discovery of America, or the introduction of the amalgam of quicksilver.