The heavens above: a popular handbook of astronomy (1882)
Gillet, J. A. (Joseph Anthony), 1837-1908 · New York, Chicago, Potter, Ainsworth, & Co. · leaf 314
Fig. 321. 292. Periodic Comets. — There are quite a number of ASTRONOMY. 287 … comets which are known to be periodic, returning to thesun at regular intervals in elliptic orbits. Some of thesehave been observed at sev-eral returns, so that their j^.,period has been determinedwith great certainty. In thecase of others the perio-dicity is inferred from thefact that the velocity…
Astronomy
Internet Archive · Cornell University Library · Public Domain Mark 1.0. Free to use for anything.
