The origin of the gold found in California seems to me to have been clearly volcanic. The varying conditions under which it is found may be accounted for by the varying heat and force of the upheaval, the different qualities of the matrix or quartz that carried the gold and filled the fissures of the veins or lodes, the influence that resistance of the inclosing walls may have exerted when it was slight or very great, and finally the disintegrating influences of air, water, frost and attrition of the glaciers, and the deposition in water. The theories of aqueous deposit (in the lodes) and of electrical action, do not satisfy my understanding, and I go back in thought to the ten years of observation and practical experience in the gold mines, and to the problems that were then but partially solved. Looking at California as it is to-day, it will be conceded that its territory has been subjected to distinct geological periods, and those periods greatly varying in their force in different parts of the State. Within the principal gold-bearing region of California, and especially along the line of or near the Carson vein or lode, coarse gold has been found, and in such large masses, free of quartz, as to force the conviction upon the mind that the gold so found had been thrown out _through_ and _beyond_ its matrix into a bed of volcanic ashes, very nearly assuming the appearance that lead might assume when melted and thrown in bulk upon an ash heap. Where the resistance was great, as when thrown through wall rocks of gneiss, or green stone, the liquefaction of the quartz seems to have been more complete, and the specific gravity of the gold being so much greater than that of the quartz, its momentum, when in large quantities, carried it out beyond its matrix, leaving the more diffused particles to be held suspended in the fast cooling quartz, or to settle into “pockets,” or small fissures. Prof. Le Conte says: “The invariable association of metaliferous veins with metamorphism demonstrates the agency of heat.” Experiments of Daubre and others prove that water at 750° Fahr. reduces to a pasty condition nearly all rocks. Deposits of silica in a gelatinous form, that hardens on cooling, may be seen at some of the geysers of the Yellowstone; the heat, no doubt, being at a great depth. Quartz, like glass and lava, cools rapidly _externally_ when exposed to air, or a cool surface, and would very readily hold suspended any substance _volatilized_, or crudely mixed into its substance. Its difficult _secondary_ fusion is no obstacle to a belief in the capacity of heat under great pressure, to account for the phenomena that may be observed in the gold mines. Ashes derived from lavas have been found rich in crystalline substances. Crystals and microliths, and pyrites in cubes are, no doubt, of volcanic origin. The eruptions of moderate character seem to be the result of igneous fusion, while those of an explosive type are probably aquæ-igneous.