Because when you take out that last piece of gold -- and they did incredibly quickly. I mean, if you look at the 1849 Gold Rush -- the entire American river region, within two years -- every stone had been turned. And after that, only big companies who used more sophisticated mining technologies started to take gold out of there.
最後の金塊を掘り出した後に 1849年のゴールドラッシュを見ればわかるように アメリカの河川領域にある石が ２年の間にすべて裏返され その後 洗練された採鉱技術を持つ 大会社が採掘を始めたのです