1905  . . . prospectors have been deterred from going into the country because of the lack of transportation facilities, which are absolutely necessary to the success of lode-mining.
1952  Lode mining, depending on heavy equipment, is now predominant in the industry.
1963  In this period of 10 years, the working force in the lode-mining industry has been reduced from 9610 to 3993. . . .