The quicksilver mines of California are believed to be numerous, extensive, and very valuable. The largest and most profitable one yet opened is situated near San José, and belongs to, or is claimed by, Mr. Forbes, of Tepic, in Mexico. The cinnabar ore, which produces the quicksilver, is easily procured, and machinery has been put in operation, which enables the proprietor to make an extensive profit. The value of the quicksilver mines, by being so near the gold region, is considerably increased; quicksilver being almost indispensable in gold mining. Extensive beds of silver, iron, and copper ores are believed to exist in the territory, but their existence and value is not accurately ascertained, the allurements held out by the continued success of the gold-miners and the continued discovery of new and profitable _placers_ being too strong to permit any search for the baser, but more useful metals. Respecting the propriety of the establishment of a mint in California, Mr. King makes the following observations-- "I have already alluded to the propriety of establishing a mint in California. This is important in many respects. At this time, there is not coin in the country to supply a currency. Much difficulty is experienced in procuring enough to pay the duties on imported goods. The common circulating medium is, therefore, gold dust, which is sold at $15 50 to $16 per ounce. In the mines, it is frequently sold much lower. The miners, the laboring men, are the sufferers from this state of things. "Those who purchase and ship gold to the Atlantic States make large profits: _but those who dig lose what others make_. "I have estimated that there will be $50,000,000 collected during the current year. At $16 per ounce, that sum will weigh 3,125,000 ounces. "Gold, at the United States mint, is worth $18 per ounce, making a difference in value on that quantity, between San Francisco and New York, of $6,250,000, which would be saved to the miners by the establishment of a mint. "I have also suggested its importance as a means of promoting and increasing our trade with the west coast of Mexico and South America. "It is not doubted that the construction of a railway across the Isthmus of Panama, and, perhaps, the establishment of other lines of communication between the two oceans, will give to the products and manufactures of the older States of the Union command of the market of California to the exclusion, in a great degree, of those of the west coast. "A mint will, therefore, become of the utmost importance, to give such marketable value to silver bullion as to enable the merchants of those countries to keep up and increase the intercourse with our principal ports on the Pacific.