communication between capital and distant cities, increasing the power of the central Mexican state over distant regions. Dispatching Rurales quickly to troubled areas was a direct effect of more efficient communication. An industry that expanded significantly during this time was mining. In the colonial era, Mexico had mined and refined silver, minting silver coinage that became the first global currency. This silver industry had declined after independence, as the prevalent refining processes in the early 19th century (the patio process and later the pan amalgamation process) required mercury; during the colonial era, this was imported from Spain, which had been one of the world's leading producers of mercury since Roman times. However, the Spanish refused to sell the reagent to its former colonies and it was not available locally in industrial quantities. Silver mining later revived with new processes not requiring mercury, but during the Porfiriato, mining of industrial minerals became the core of the industry. The world price of silver dropped in 1873, while at the same time economies in developed countries needed industrial minerals for their manufacturing. As with other aspects of the Mexican economy, the growth in the mining sector was predicated on the stability established by the government. The expansion of the railway network meant that ore could be transported cheaply and the telegraph network allowed investors to have efficient communications with the mining sites. Foreign investors, particularly from the U.S., had confidence in risking their capital in mining enterprises in Mexico. Mining enterprises for copper, lead, iron, and coal in Mexico’s north, especially Sonora, Chihuahua, Durango, Guanajuato and Coahuila, with Monterrey and Aguascalientes becoming especially prominent. The development of industrial manufacturing aimed at a domestic market, primarily in textiles. Factories were built in urban areas by Mexican entrepreneurs in Orizaba and Guanajuato, which provided opportunities for workers to earn wages. These factories, many owned by French nationals, supplied domestic textile needs. Furthermore, these factories were steam-powered, capitalizing on modern invention. Labor Craft artisan organizations already existed when Díaz came to power in 1876, as mutualist organizations or worker benevolent societies, and conducted strikes. The Gran Círculo de Obreros de México had nearly 30 branches in Mexico, calling for benefits beyond aiding of workers when they were sick, injured, or died. In 1875, the Congreso Obrero sought broader goals, including education for adult workers, compulsory education for children, and representation of their goals to authorities. The