'48 , MINERAL RESOURCES.
complicated hydraulic mining replacing placer workings and vein t mining becoming gradually more developed. The first great silver producer, the Oouistock lode, was opened during this decade, and from this and other smaller bodies -of rich silver ore, whose discovery was a more or less direct consequence of its development, the silver product increased gradually during the decade from $1,000,000 to $10,000,000. Toward the end of the decade the first great silver-ore bodies in limestone were discovered, the first smelting works in the western mountain region were established, and the first transcontinental railroad line was built, circumstances which were to have a most.important and far-reaching influence upon the mining industry.
During 187Q-'80 the mining industry was gradually being established on a more permanent and business-like basis through the introduction of improved methods and machinery and the increase in"transportation facilities. Placer mining was almost entirely conducted on the hydraulic' system, which involved a considerable investment of outside capital and the concentration of the workings into fewer hands. Prospectors were turning their attention more and more to the discovery of base-metal ores whose principal value is in silver rather than gold, and which, being more likely to develop into great bonanzas like the jComstock, were hence more attractive to capitalists. Gold mining proper settled down to a comparatively regular output, but the gold product of the ,country was kept up by the Oomstock lode, two-fifths of whose bullion .value was in gold. This remarkable deposit readied the climax of its product during the decade, contributing during five years an average of $25,000,000 to $30,000,000 annually to the precious-metal product of the country. The silver product during the decade increased steadily from $12,000,000 to $30,000,000, while that of gold fluctuated between $33,000,000 and $50,000,000.
The opening of the decade 1880-'90 witnessed the final transference of the center of activity of mining in the West from J;he Sierra Nevada to the Rocky mountains. The bonanzas of the Oomstock lode had been exhausted, and its deeper workings were soon to be abandoned as unprofitable. The reduction in the silver product caused thereby was more than replaced by the recently discovered silver-lead deposits in limestone of the Leadville district, which, however, carried little or no gpld. The ultimate importance of the discovery of these ores, and of the many similar, ones since opened as a direct result of the teachings their development has aiforded to the mining community, has been shown in the enormous development of the smelting industry, and the "concomitant opening of coal fields and the building of railroads in every direction through the mountain region, which, in turn, have stimulated the opening of silver mines carrying mixed or low-grade ores wherever they could be found within reach of railroads.
The characteristic feature has been the increase of railroad facilities throughout the mining region and the enormous development of the smelting industry, which is thus far the highest development of technical