Jupiter is of enormous proportions. Its equatorial diameter measures 88,000 miles, and its circumference no less than 276,460 miles, these dimensions being 11 times greater than those of the Earth. This planet, notwithstanding its huge size, rotates on its axis in not far from 9h. 55m. 36s., which period constitutes its day. Owing, however, to the changeable appearance of its surface, this period cannot be ascertained with very great exactitude. In consequence of its rapid rotation, the planet is far from spherical, its polar diameter being shorter than the equatorial by about ¹⁄₁₆, or 5,500 miles. Its surface is 124 times the surface of the earth; while its volume is 1,387 times as great. If Jupiter occupied the place of our satellite in the sky, it would appear 40 times as large as the Moon appears to us, and would cover a surface of the heavens 1,600 times that covered by the full Moon, and would subtend an angle of 21°. Jupiter's mass does not correspond with its great bulk, and is only ¹⁄₁₀₄₇ of the mass of the Sun, and 310 times the mass of the earth; its density being only ¼ of that of our globe. The force of gravitation at the surface of this planet is over 2½ times what it is on the Earth, so that a terrestrial object carried to the surface of Jupiter would weigh over two and a half times as much as on our globe. Observed with a telescope, even of moderate aperture, Jupiter, with its four attending satellites and its dazzling brilliancy, appears as one of the most magnificent objects in the sky. The general appearance of the disk is white; but unlike that of Mars, it is brightest towards its central parts, and a little darker around the limb, especially on the side opposite to the Sun. Although an exterior planet, and so far from us, Jupiter shows faint traces of phases when observed near its quadratures, but this gibbosity of its disk is very slight, and is indicated only by a kind of penumbral shadow on the limb. When observed with adequate power, the disk of Jupiter is found to be highly diversified. The principal features consist of a series of alternate light and dark streaks or bands, disposed most of the time parallel with the Jovian equator. These bands differ from each other in intensity as well as in breadth; those near the equator being usually much more prominent than those situated in higher latitudes north and south.