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190 that there may be none on the outside for us to detect, but there may be some in the interior; and accordingly he puts the dwellings down inside the Moon, so that the people can breathe. But he allows some air for the outside, and he brings it into the story in a very interesting way, all frozen. The "first men in the Moon " land in a regular snow-drift of frozen air, due to the fact that they land on a part of the surface on which the Sun is not shining, so that it is bitterly cold—so cold as to freeze the air. Not very long ago no one had ever seen air frozen or even liquid; but you fortunate young people of to-day can have it shown to you quite easily, and we will conclude this lecture with one or two experiments showing liquid air.

Here is a regular fountain of it at the back of the room. It is frightfully cold, and though it will not hurt you to put your hand in it for a moment, you could easily burn the skin off your hands by exposing them to it for too long. If we put an india-rubber ball into liquid air it is frozen so hard that it breaks when we throw it down. Even a flower dipped into liquid air becomes quite brittle. But perhaps the prettiest effect of liquid air can be seen by pouring some into a bath of warm water (see illustration). It makes a beautiful snowy cloud over the surface of the water. Now if some of the audience will kindly take these fans and fan away that cloud, they will find underneath little frozen cakes of air, bubbling furiously. One can show that they are cakes of air by the effect on a glowing wooden pipelight; we will light such a pipelight or a big wooden match: then blow out the flame, but leave the end glowing.