Miscellaneous Papers (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1896 edition. Excerpt: ...point of contact and the planet's equator being estimated at about thirty degrees. The satellite retained its shape until almost in contact with the limb, when the major axis of its ellipse suddenly changed its position angle through thirty degrees, becoming parallel to the limb of the planet. Now the interest of this observation lies in the fact that this is just the sort of change that we should expect would be produced if Jupiter were surrounded by a comparatively rare atmosphere, extending several hundreds of miles above its surface, such as presumably extends several thousand miles above the suface of the Sun and thirty or forty miles above that of the Earth. The observation is a very difficult one, however, and whether the change of shape was real or only apparent must be settled by subsequent research. The following ephemeris for the month of March, 1893, gives the approximate Greenwich mean time at which this satellite presents the smaller of its two elliptical phases, that is, the one in which the minor axis is parallel to the plane of its orbit. Under these circumstances it shines with its minimum brilliancy. Third Satellite.--On account of its size and brightness this is much the easiest satellite to observe. Indeed even the occasionally elliptical shape of its disc has been noted by Lassell, Secchi and Burton. None of these observers, however, seem to have been able to repeat their observations with sufficient frequency or precision to construct an ephemeris from them, or determine the inclination of the axis. When the disc is most elliptical the major axis exceeds the minor by about 0."2, a very appreciable quantity. The satellite appears to be of the shape of an oblate spheroid (like a watch), revolving about one of its major...