As may readily be conjectured, every stream and ravine in the valley of the Sacramento was soon explored. Gold was found on every one of its tributaries; but the richest earth was discovered near the _Rio de los Plumas_, or Feather River,[5] and its branches, the Yuba and Bear rivers, and on Weber's creek, a tributary of the American Fork. Explorations were also made in the valley of the San Joaquin, which resulted in the discovery of gold on the Cosumnes and other streams, and in the ravines of the Coast Range, west of the valley, as far down as Ciudad de los Angeles. In addition to the gold mines, other important discoveries were made in Upper California. A rich vein of quicksilver was opened at New Almaden, near Santa Clara, which, with imperfect machinery,--the heat by which the metal is made to exude from the rock being applied by a very rude process,--yielded over thirty per cent. This mine--one of the principal advantages to be derived from which will be, that the working of the silver mines scattered through the territory must now become profitable--is superior to those of Almaden, in Old Spain, and second only to those of Idria, near Trieste, the richest in the world. Lead mines were likewise discovered in the neighborhood of Sonoma, and vast beds of iron ore near the American Fork, yielding from eighty-five to ninety per cent. Copper, platina, tin, sulphur, zinc, and cobalt, were discovered every where; coal was found to exist in large quantities in the Cascade range of Oregon, of which the Sierra Nevada is a continuation; and in the vicinity of all this mineral wealth, there are immense quarries of marble and granite, for building purposes. Colonel Mason had succeeded Colonel Fremont in the post of governor of California and military commandant. A regiment of New York troops, under the command of Colonel Stevenson, had been ordered to California before the conclusion of the treaty of peace, and formed the principal part of the military force in the territory. Colonel Mason expressed the opinion, in his official despatch, that "there is more gold in the country drained by the Sacramento and San Joaquin rivers, than will pay the cost of the [late] war with Mexico a hundred times over." Should this even prove to be an exaggeration, there can be little reason to doubt, when we take into consideration all the mineral resources of the country, that the territory of California is by far the richest acquisition made by this government since its organization. The appearance of the mines, at the period of Governor Mason's visit, three months after the discovery, he thus graphically describes: