Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: Section IV. Theory of Jupiter's Satellites—Effects of the Figure of Jupiter upon hit Satellites—Position of their Orbits—Singular Laws among the Motion! of the first three Satellites—Eclipses of the Satellites—Velocity of Light —Aberration—Ethereal Medium—Satellites of Saturn and Uranus. The changes which take place in the planetary system are exhibited on a smaller scale by Jupiter and his satellites; and, as the period requisite for the development of the inequalities of these moans only extends to it few centuries, it may be regarded as an epitome of that grand cycle which will not be accomplished by the planets in myriads of ages. The revolutions of the satellites about Jupiter are precisely similar to those of the planets about the sun: it is true they are disturbed by the sun, but his distance is so great, that their motions are nearly the same as if they were not under his influence. The satellites, like the planets, were probably projected in elliptical orbits : but, as the masses of the satellites are nearly 100,000 times less than that of Jupiter; and ns the compression of Jupiter's spheroid is so great, in consequence of his rapid rotation, that his equatorial diameter exceeds his polar diameter by no less than 6000 miles; the immense quantity of prominent matter at his equator must soon have given the circular form observed in the orbits of the first and second satellites, which its superior attraction will always maintain. The third and fourth satellites, being farther removed from its influence, revolve in orbits with a very small eccentricity. And although the first two sensibly move in circles, their orbits acquire a smSll ellipticity, from the disturbances they experience (N. 86). It has been stated, that the attraction of a sphere on nn exterior body is ...