THE history of Nevada can roughly be divided into four twentyyear periods, each of them more or less coinciding with a mining cycle. The first period was characterized by the discovery and mining of the Comstock Lode and other deposits of silver and gold, some unbelievably rich and others of less importance. The next period saw a rapid decline in mining as a result of the exhaustion of rich deposits and the demonetization of silver. The third period, which began with the great silver discovery at Tonopah, followed by jewelry-ore gold at Goldfield, copper at Ely, and many scattered strikes of lesser value, continued to be highly profitable even after the richest silver and gold mines became unproductive, for the outbreak of war in Europe created a demand for many Nevada minerals.
At the beginning of the fourth period there was another rapid decline in demand, as well as a lack of large known deposits of ore rich in silver and gold. The price of silver, which had risen during the war above its 1873 level, dropped a third within a year. But the pattern of the second period, with its great loss of population and virtual cessation of mining activity, was not repeated. Introduction of the cyanide recovery process saved the day. Up to about 1921 nearly all silver and gold recovery in Nevada had been by the ancient amalgamation process, in which the values were extracted from pulverized silver ores by amalgamizing the metal with mercury; the mercury was afterward expelled. This process recovered only part of the values, sometimes less than half. The cyanide process, invented in 1887 to enable more complete recovery of gold, and later tried on silver ores, had been little used in the State. Although more expensive than the amalgamation process, it enabled the profitable working of low grade ores and the reworking of old tailings. Copper, undiscovered at the time of the first mining collapse, also gave considerable income in the post-war period, though profits dropped sharply.
The international price of silver continued to decline after 1921 and in 1932 reached an all-time low of 241/2 cents--with an average for the