EVERYBODY notices, year by year, in a southerly direction, a bright star which half the spectators believe to be the evening star, but which so far from being Venus, is its very antithesis. To mistake Jupiter for Venus is a sufficiently gross error. But even this error is preferable to nothing. It is better to be mistaken than not to see anything. A large portion of the human race sees nothing at all, thinks nothing, and passes its whole life in the stupidity of plants and slugs. To notice the star in the sky, even to give it a wrong name, is something, at all events. It shows that one does not go about with eyes cast on the ground or occupied with worldly affairs and with the spirit absorbed by material interests. Venus, the Shepherds’ Star, the morning and evening star, is never far from the sun. It is never in the south, neither in the evening nor at midnight. Its orbit round the Sun lies within our own. Jupiter, on the contrary, revolves round the same Sun along an orbit outside our own, five times as far as the central luminary, at 485 million miles instead of 92 million miles. The distance between us and Jupiter is therefore always greater than 393 million miles except when the Earth reaches the extremity of its elliptical orbit (“aphelion”) at a time when Jupiter is in “opposition” to the Sun. We often see it at a medium distance of 450 million miles. If the atmosphere extended over all that distance, an aeroplane flying without a stop at 62 miles an hour, and therefore covering 1,500 miles a day, would take no less than 300,000 days or 812 years to complete the voyage. It would be wise to take some provisions with us! But on what sort of a world should we arrive? A giant world, an immense world, a strange world. It is only a thousand times smaller than the Sun--that is to say, 1,000 times larger than the Earth, or even more. Jupiter is eleven times larger in diameter than our globe, i.e. 1,300 times larger in volume. Gravitation is enormous at its surface, 2½ times what it is here. A man weighing 10 stone here would weigh 25 stone there. But its density is very low, being one-quarter of that of the earth. It is a world of water and more or less dense gas. Astronomers observe it with great interest since they see it furrowed with various currents and enveloped in clouds and vapours. The currents at the surface revolve with different speeds, so that it is difficult to know what is the rotation of the planet itself. At the equator, this rotation is accomplished in 9 hours 50 minutes 30 seconds; not far from the equator, in the subtropical regions, it takes 9 hours 55 minutes 41 seconds. Since Jupiter’s year is twelve times as long as ours, there are more than 10,000 days per annum.