the largest of all the planets; larger, indeed, than all the other planets put together. Viewed in the telescope, the surface of Jupiter is usually seen crossed by two belts, one above and one below his equator. You would produce something like them on any ordinary globe by making a broad belt on the tropic of Cancer, and another on the tropic of Capricorn. Now, these belts on Jupiter are not fixed features of his surface; they are constantly changing their aspect. Sometimes they are hardly to be seen at all, and on other occasions they widen their limits and become irregular at their edges; the greater part of the surface of the planet is more or less covered over with similar markings. We see nothing on this great planet that resembles the oceans and continents on Mars, nor have we any indications of arctic regions on Jupiter's surface. In fact, the longer we look at Jupiter, the more we become convinced that the surface of the planet is swathed with a mighty volume of clouds so dense and so impenetrable that our most powerful telescopes have never yet been able to pierce through them down to the solid surface of the planet. Indeed we can hardly say whether this planet has any solid interior at all. There is one object on Jupiter known as "the great red spot," which for several years was more or less recognisable. This seemed to be a great volcano, or some other projection from beneath, which was tall enough and large enough to make itself visible through the mighty covering of clouds which act as an effectual screen to hide all objects of lower prominence.
There is another very interesting way in which we can confirm the fact that the apparent volume of Jupiter is swollen by these mighty clouds which so closely encase
