Yet even at the very best, when the moon is brought, as one may say, within perhaps a hundred miles of the Earth, even then one can only see large things on her surface, not small things. A man who climbs a high mountain gets a wide view all round from the top. He may see perhaps a hundred miles in one direction. But at that distance, and at a good deal less than that distance, he cannot make out much. A mountain or a high hill is pretty clear, perhaps, or the glimmer of a big lake, and a large town would be just visible as a tiny patch or spot. A single house could not be seen at all; far less a horse or a man. However, though we could not possibly see such small things as these upon the Moon if they were there, we are very sure that no houses _are_ there, and no horses, and no men. And the reason why we are so sure is that the Moon has no air. A man cannot live without air, because he cannot breathe. Try holding your breath for a little while and you will find how soon you must begin breathing again. If there were no air in your room you would soon die of suffocation. Animals cannot live without air. Even fishes need air in the water to keep them alive. And it seems that there is neither air nor water in the Moon. No air: or almost none; if any at all, it is so very thin that no living creature on earth could breathe it. No water; no seas or oceans; no rivers and streams. No clouds; for clouds are made of water and float in air. No grass, or plants, or trees; for they too must have air and water. No towns or villages; for they are built by man, and no men can be on the Moon, or women or children. What a dreary place the Moon must be! It looks dreary seen through a big telescope. It looks dreary also in a photograph. Many photographs are now taken of the Moon. Such a wild lonely scene we find! Flat desolate plains, and mountains with sharp black shadows and clefts and streaks, and a great number of craters in all directions. You have heard of volcanoes on the Earth. A volcano is a mountain, shaped usually something like a sugar-loaf, with a cup-like hollow near the top. This hollow is called a _crater_: and now and then fire pours from it, with melted burning rocks, or boiling mud, or hot cinders. In parts of the world there are old used-up volcanoes, which once were very active indeed but which now have no outbreaks. We call these dead volcanoes. The Moon seems to be half covered with the craters of volcanoes. That side which we always see is pitted over with round holes, big and little--looking in parts almost like a face badly marked with small-pox. If all these holes really are craters they must belong to _dead_ volcanoes; because not a sign is ever observed of any fiery outburst on the Moon. That could easily be seen through a large telescope. These craters are of all sizes: and many of them have been measured from the earth.