It was known that mines of the precious metals existed to a considerable extent in California at the time of its acquisition. Recent discoveries render it probable that these mines are more extensive and valuable than was anticipated. The accounts of the abundance of gold in that territory are of such an extraordinary character as would scarcely command belief were they not corroborated by the authentic reports of officers in the public service who have visited the mineral district and derived the facts which they detail from personal observation. Reluctant to credit the reports in general circulation as to the quantity of gold, the officer commanding our forces in California visited the mineral district in July last for the purpose of obtaining accurate information on the subject. His report to the War Department of the result of his examination and the facts obtained on the spot is herewith laid before Congress. When he visited the country there were about 4,000 persons engaged in collecting gold. There is every reason to believe that the number of persons so employed has since been augmented. The explorations already made warrant the belief that the supply is very large and that gold is found at various places in an extensive district of country. Information received from officers of the Navy and other sources, though not so full and minute, confirms the accounts of the commander of our military force in California. It appears also from these reports that mines of quicksilver are found in the vicinity of the gold region. One of them is now being worked, and is believed to be among the most productive in the world. The effects produced by the discovery of these rich mineral deposits and the success which has attended the labors of those who have resorted to them have produced a surprising change in the state of affairs in California. Labor commands a most exorbitant price, and all other pursuits but that of searching for the precious metals are abandoned. Nearly the whole of the male population of the country have gone to the gold districts. Ships arriving on the coast are deserted by their crews and their voyages suspended for want of sailors. Our commanding officer there entertains apprehensions that soldiers can not be kept in the public service without a large increase of pay. Desertions in his command have become frequent, and he recommends that those who shall withstand the strong temptation and remain faithful should be rewarded. This abundance of gold and the all-engrossing pursuit of it have already caused in California an unprecedented rise in the price of all the necessaries of life.