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140 that liquid air may give a beautiful snowy appearance, and it is possible that the Martian polar caps are not made of ice and snow but of liquid air or frozen carbonic acid gas, or some other gas which on the very cold surface of Mars becomes liquid or even solid.

There are other markings on the picture, but what you will probably look for are the famous canals of Mars. I am afraid there are none shown on this picture because Mr. N. E. Green, who made it, did not see any canals. Some people do not see them, and claim that therefore they cannot be there. One scarcely knows what to say about this claim: it is rather like calling witnesses, after others have testified that they saw a theft committed, to declare that they did not see the theft. We should probably pay more attention to the first lot who saw something and agreed among themselves about it. Nevertheless, we must be careful to listen to the others also, in case there is more in what they say than might appear at first. A jury must be very careful before they find a man guilty, and one thing they must be specially careful about is not to let their feelings of affection or dislike influence them. So well known is it that such feelings may interfere with true justice that every effort is made to have the jury composed of people who do not know the prisoner being tried, because a friend might interfere with justice in one way or an enemy in the other. Now in this case of the canals of Mars it is rather harder than usual to keep the friends and enemies off the jury. Some people are very anxious to believe that the planets are inhabited and they are inclined to jump at