From B.C. 1768 to A.D. 532, 69 periods of 33·319 years each. " A.D. 532 to " 599·5, 2 " 33·750 " " " 599·5 to " 902, 9 " 33·614 " " " 902 to " 934, 1 " 32·000 " " " 934 to " 1002, 2 " 34·000 " " " 1002 to " 1101, 3 " 33·000 " " " 1101 to " 1202, 3 " 33·667 " " " 1202 to " 1366, 5 " 32·800 " " " 1366 to " 1533, 5 " 33·400 " " " 1533 to " 1698, 5 " 33·000 " " " 1698 to " 1799, 3 " 33·667 " " " 1799 to " 1833, 1 " 34·000 " " " 1833 to " 1866, 1 " 33·000 " The first three dates are alone doubtful. The whole number of intervals from B.C. 1768 to A.D. 1866 is 109, and the mean length is 33·33 years. The perturbations of the ring by Jupiter, Saturn, and Uranus, are doubtless considerable. It is worthy of note that-- 14 periods of Jupiter are nearly equal to 5 of the ring. 9 " Saturn " " 8 " 23 " Uranus " " 58 " This group or stream has its perihelion at the orbit of the earth; its aphelion, at that of Uranus. (See diagram, p. 24.) It must therefore produce star-showers at the latter as well as at the former. Our planet, moreover, at each encounter appropriates a portion of the meteoric matter; while at the remote apsis of the stream Uranus in all probability does the same. The matter of the ring will thus by slow degrees be gathered up by the two planets. B. Comets and Meteors. The recent researches and speculations of European astronomers in regard to the origin of comets and of meteoric streams, have suggested to the author the propriety of reproducing the following extracts from an article written by himself, in July, 1861, and published in the _Danville Quarterly Review_ for December of that year: