With so dense an atmosphere as Jupiter most likely has, it is sometimes doubtful whether his surface can be seen by us at all. But it is certain that we see something apparently much more dense and stable than an atmosphere is supposed to be; and hence it is thought that, in spite of its thickness, the atmosphere may be only partially opaque, and that it may be in some places even more or less transparent. It does not seem probable that the markings on Jupiter are wholly atmospheric. Some of them indicate that the substance we see has considerably more consistency than a mere gas. The whole surface of the planet is covered with belts and spots of various colors and varying shapes. The belted appearance is particularly marked. It has been noticed for more than two hundred years, and can be seen with a comparatively small telescope. Sometimes as many as twenty or thirty belts have been seen at one time. All of them are parallel with the equator. Two broad red belts on each side of the equator, called the tropical belts, are very distinct, and sometimes retain the same shape and color for months at a time, though sometimes they change rapidly in both color and outline. Between them is the equatorial belt, which is also a semi-permanent feature, remaining often for a considerable period unchanged. These belts, and the spots that sometimes appear on and near them, have been closely watched, because about the equator, and especially just south of it, is the region of greatest activity on Jupiter’s surface. One feature that more nearly suggests solidity and permanency than anything else on Jupiter is the famous great red spot which lies in the southern hemisphere just below the southern tropical belt. It appeared about thirty-five years ago, in July, 1878, as a pale pink spot, grew brighter for two or three years, and then faded, until, at the end of two or three more years, it was almost invisible. In another year it came again, and increased in brightness for five or six years. Then it grew a little fainter, and has since remained a rather faint red spot, but plainly visible. In shape the great red spot is an immense oval as much as thirty thousand miles from east to west and seven thousand miles from north to south, which gives it a surface four or five times as large as the land area on the entire earth, and larger even than the whole surface of the earth including the oceans. Although retaining its own shape, it seems to drift about among its surroundings, showing that it is not attached to any solid surface; and yet it has a suggestion of solidity in itself, which was shown when it and another smaller spot were seen to be drifting toward each other, and then finally to meet. Instead of colliding or going over or under, they calmly drifted to one side and went around each other.