[填空题]
Clocks through Time
It took human being a long time to invent diverse ways for telling time. About 3000 years ago people first made a circle with a stick in the center of it to
(1) the passage of time by noticing various marks on the circle the shadow of the stick fell across.
Since these kinds of circles that are called
(2) did not work without the sun, men had to find other ways to keep track of time, including a
(3) candle on which each stripe took about one hour to melt, a water clock which had a line with a number beside it for every hour and an
(4) which followed the invention of glass blowing.
The first clock with a face and an hour hand was invented about 600 years ago for few people. With the gradually
(5) use of clocks, they were beautifully
(6) , though they could not keep correct time. Scarcely had clocks been made small enough to be carried when
