and we have to lower into the ground and haul out of the ground great lengths of drill pipe which are rotated by an engine at the top and are fitted with a cutting bit at the bottom.
我們必須把很長的鉆桿一節(jié)節(jié)地鉆入地下,然后再從地下拉出來。鉆桿頂部安裝的發(fā)動機(jī)帶動鉆桿旋轉(zhuǎn),它的底部裝有鉆頭。