The illustrated London astronomy
John Russell Hind
Paperback
(RareBooksClub.com, March 6, 2012)
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. 1853 Excerpt: ...by inadvertently omitting to add a dark glass, or from its being suddenly broken by the concentration of the Sun's rays upon it. It is only of recent date that means have been devised by which the large telescopes in observatories can be brought to bear with advantage upon the solar phenomena; one singular result of this practical improvement has been the discovery of a gyratory or revolving motion of the spots themselves, independent of their apparent movement across the disc. It has also been surmised that some of these objects undergo a real change of position upon the surface of the Sun, since the times of rotation given by different spots often differ more than can be accounted for by errors in the observations. Besides the dark spots, there are others of a more luminous character than the general surface, presenting themselves commonly in the form of bright streaks near those parts where the black spots actually exist, or where they have recently disappeared: these are called faculce. When examined with a good telescope, the whole disc of the Sun is found to be covered by minute shady dots, which give his surface a mottled appearance. It frequently happens that they seem to be undergoing rapid changes; but it is most likely that this is caused by the variable conditions of the Earth's atmosphere, and consequently is only apparent. To explain the phenomena of the spots, it is thought by astronomers that the body of the Sun is dark, and that parts of it are rendered visible to us by openings in his atmosphere, through the action of currents, or some analogous agency. These visible portions form the black centres of the spots; the lighter shades surrounding them are assumed to be the cloudy stratum or interior envelope of the Sun, while the penumbra is p...