The planet Venus had been shining brilliantly evening after evening. “Why, father,” said the boy, “does Venus shift her place so rapidly among the stars?

Because she has to travel round the sun, as the world and other planets do.

And is the world really a planet, looking like a star to the people of Venus?

Yes; and not visible at all to those of the distant planets, which are all so much nearer to us than the nearest of the fixed stars. Some of the planets you could not see without the telescope, and you see none of the asteroids.

What are they?

Little planets, over eighty in number, perhaps the shattered parts of an exploded planet, travelling along the old road, and keeping a circle between Mars and Jupiter.

Then they are not like the comets, which run everywhere, getting in everybody’s way?

You are slandering the comets. These shadowy bodies, with tails of light, travel in longer ovals or ellipses than the planets. We see them when they turn round the sun, which is n............