Ancient man attempted to change the weather by using
magic. While experience taught him this was impossible, __1__
he tried to forecast weather conditions. Even earlier in __2__
1000 B.C.there were weather seers in Babylon----and
priests clever enough to denounce as frauds those predicted __3__
the weather a year in the advance. Some forecasters used __4__
methods that seemed to take no connection with the actual __5__
factors controlled the weather. Chickens and other animals __6__
were sacrificed and their intestines poked to find signs
indicating rain and drought. Somewhat more scientific were __7__
predictions based on vegetation:"Onion's skin very thin ,mild
weather coming in. Onion's skin thick and tough, coming
weather is cold and rough." Insects and animals were also __8__
favorite weather clues: "Before the glowworm lights his __9__
lamp , then the air is always damp ." "If spiders their cobwebs
forsake , the weather will for certain break ." "If frogs remained
in pools , the weather will be fine . If they were seen on rocks, __10__
rain and cold were due." It's difficult to say whether this rhyme
should be taken seriously : " Hark , I hear the asses bray . Me thinks
we'll have some rain today ."

答案及解析:
1.While—When或After
本句的this指代的是to change the weather by using magic. when/after 引导时间状语

2.in—than
earlier是early的比较级，其后应有than

3.those之后加who
who引导定语从句

4. 删除advance前的the
in advance为习语

5. take—have
have connection with 为习语

6. controlled—controlling或在controlled前加that/which
controlling the weather 或that/which controlled the weather做定语修饰the actual factors

7. and—or
rain和draught只能是二者之一

8. 删除is
与上文平衡，均为省略句

9. before—when/if
条件句

10. will—would
if引导的是条件句用的是remained一般过去时