Falling back, this debris heated the air to the temperature of the inside of an oven.

这些碎片落下来后，把空气加热到烤箱内部的温度。

But at the same time, we need fans to be moving that heated and now more humid air.

但同时，我们也需要风扇来吹动那些升温潮湿的空气。

As the sun rose higher, the heated air began to flow in tremulous waves from every southern slope.

随着太阳升得更高， 加热的空气开始以颤抖的波浪形式从每个南坡流动。

I could not believe my own eyes; but the heated air and the sensation of burning left me no room for doubt.

我简直不敢相信自己的眼睛；但炎热的空气和灼热的感觉让我毫无疑问。

Very good. You then understand that cold air is heavier than the heated air, as that iron is heavier than the water; so now we will go back to the main question-what makes the smoke go upwards?

太对了，这样，你就明白了冷空气比暖空气重，正如铸铁套比水要重是一个道理。现在，我们再回到主要问题，烟怎么会上升呢？