1.
An airship depends on a gas that is lighter than air.
而飞艇依靠的是一种比空气轻的气体。
2.
A self - propelled lighter - than - air craft with directional control surfaces.
飞艇，飞船自身驱动且比空气轻的飞行器，有方位控制平面
3.
"Hot air is lighter than colder air," they said. "That is why hot air goes upwards.
他们说：“热空气比冷空气轻，因而热空气会向上升。
4.
Hydrogen is a useful gas for balloons. It is lighter than air.
氢气对于气球来说是一种有用的气体，它比空气轻。
5.
Suggestive of air, as in lightness;airy.
轻如空气的在轻度上使人想起空气的；轻而薄的
6.
A momentary stirring of air.
轻拂空气的瞬间搅动
7.
It is less dense and lighter than an equal amount of cool air.
这样，它的密度就比同样数量的冷空气要小，因而重量也更轻。
8.
Children use more food, air and water than adults do in relation to their body weight.
相对于他们较轻的体重，儿童比成年人消耗更多的食物、空气和水。
9.
A balloon rises because it is lighter than air.
气球之所以能够飘升，是因为它比空气轻。
10.
Being both lighter than air and nonflammable, helium is used to inflate balloons and airships.
由于既比空气轻又不可燃，氦用作充气球和飞艇。
11.
A brisk gayety was in the air.
空气里洋溢着一片轻松愉快的气氛。
12.
Why does this work? Hot air rises because it weighs less than cold air.
为什么会这样呢？这是因为热空气比冷空气轻，所以会上升。
13.
Helium is also lighter than air, but it costs a lot of money. So balloons were (and are) usually filled with hydrogen.
氦也比空气轻，但价格昂贵，因此气球过去(现在也一样)通常都装氢气。
14.
The mountain air will rejuvenate you.
山上的空气将使你变得年轻。
15.
Smoke hung suspended in the still air.
轻烟在静止的空气里悬浮着.
16.
Finally an idea struck them like a thunderbolt -- smoke rose because it was lighter than air.
最后，他们的脑海里突然产生了一个想法——烟的上升是因为它比空气轻。
17.
Then the air inside the balloon became cool and it came slowly down and gently rested on the ground.
不久，气球内的空气变冷了，它就慢慢下降，轻轻地落到地面上。
18.
In that job Ellis just coasts along and hardly lifts a finger.
艾里斯的那份工作轻松无比，不费力气。