Astronomy, a handy manual for students and others (1918)
Dyson, Frank Watson, Sir, 1868-1939 · New York, E.P. Dutton & Co. · leaf 162
ed eye ap-pearance. This comet may return in about 2000 years. By far the larger number of comets move in orbitsnot very different from parabolas, but a considerablefraction have an orbit which is sensibly elliptic. Suchcomets are periodic, and are seen at each return to THE SOLAR SYSTEM 151… … Diag. LXX.—Donatis Comet, October 1858. a period of three and a half years. This comet, thougha faint one, is of special interest, as a diminution ofits period of revolution seems to show that in itscourse it is impeded by a resistance of some kind,possibly of meteoric or gaseous matter. Halleys…
Astronomy
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