根据美国矿业局最近公布的数字,美国的选后煤量自1967年以来第一次有所回升(图1)。1972年选后煤量为293百万吨,比1971年增加了22百万吨。因为美国已进入一个空前的能源短缺时期,所以专家们认为,原煤年产量在今后10—15年内将从600百万吨增加到1,000百万吨。至于这些煤如何开采,由哪 According to a recent figure released by the U.S. Bureau of Mines, the United States’ post-election coal volume has picked up for the first time since 1967 (Figure 1). The coal output after the 1972 election was 293 million tons, an increase of 22 million tons over 1971. Because the United States has entered an unprecedented period of energy shortage, experts believe that the annual output of raw coal will increase from 600 million tons to 1,000 million tons in the next 10 to 15 years. As for how the coal is mined, where is it?