In 1929, three years after his flight over the NorthPole, the American explorer, R.E. Byrd, successfullyflew over the South Pole for the first time. Though,at first, Byrd and his men were able to take a greatmany photographs of the mountains that lay below,they soon ran into serious trouble. At one point, itseemed certain that their plane would crash. Itcould only get over the mountains if it rose to10,000 feet. Byrd at once ordered his men tothrow out two heavy foodsacks. The plane wasthen able to rise and it cleared the mountains by 400 feet. Byrd now knew that he wouldbe able to reach the South Pole which was 300 miles away, for there were no more mountains insight. The aircraft was able tofly over the endless white plains without difficulty.
精讲笔记：
4. It could only get over the mountains if it rose to 10,000 feet.
只有在飞机飞至10,000英尺的高度时，它才能飞过这些山头。
语言点 本句包含“only + if”的结构，意为“只有……才……”。
The soldiers could only march to the next town if the rain stopped.
这些士兵们只有等到雨停了才能够行军到下一个城镇。
5. Byrd at once ordered his men to throw out two heavy food sacks.
伯德马上命令他的助手们把两个沉重的食物袋扔掉。,
语言点 order sb. to do sth.为不定式作宾语补足语的典型结构(请参考Lesson 11P)。
6. The plane was then able to rise and it cleared the mountains by 400 feet.
于是飞机上升了，在离山头400英尺的高度飞越了过去。
语言点 by在此句中表示相差的距离，并非表被动或者“在……旁边”。
