We have no data, as yet, from which to judge of the richness of the Californian and Australian sands, compared with those of Siberia. And, if we had, no safe conclusion could be drawn from them as to the prolonged productiveness of the mines, in consequence of another interesting circumstance, which the prosecution of the Uralian mines has brought to light. It is in every country the case that the richest sands are first washed out, and thus a gradual falling off in every locality takes place, till spot by spot the whole country is deserted by the washers. We give an example of this falling off in four of the Ural mines in five successive years. The yield of gold is in solotniks from the 100 poods of sand— I. II. III. IV. 1825, 2.28 sol. 1.56 sol. 5.64 sol. 1826, 1.43 „ 0.83 „ 2.46 „ 7.28 sol. 1827, 0.64 „ 0.77 „ 1.43 „ 5.0 „ 1828, 0.58 „ 0.29 „ 1.92 „ 3.52 „ As all the Ural diggings exhibit this kind of falling off, it has been anticipated, from time to time, that the general and total yield of gold by the Siberian mines would speedily diminish. But so far have these expectations been disappointed, that the produce has constantly increased from 1829 until now. On an average of the last five years, the quantity of gold yielded by the Russian, and chiefly by the Siberian mines, is now greater than that obtained from the South American gold mines in their richest days.[17] While, therefore, it is certain that the new American and Australian diggings will individually, or on each spot, become poorer year by year, yet, as in Siberia, the extension of the search, and the employment of improved methods, may not only keep up the yield for a long period of years, but may augment the yearly supply even beyond what it has yet been.