Page:The story of the comets.djvu/289

XV. periods than 80 years move in the order of the signs of the Zodiac, or "direct" (+). The 2 exceptions are Halley's Comet and the "Comet of the Leonid or November Meteors". The long-period comets and the parabolic and hyperbolic comets show a slight preponderance for Retrograde Motion (-), or motion contrary to the order of the signs of the Zodiac.

As an incidental matter of statistics, A. S. Herschel remarked on the rarity of the near approach of comets to the Earth's orbit. He found that of 80 new comets observed between 1872 and 1892, only 2 came at all near to the orbit of the Earth, namely the Comets of 1881 (v.) and 1886 (vii.). These came within about 3,000,000, and 4,600,000 miles respectively of the Earth's orbit, but these distances were not sufficiently small for a Meteor shower to be visible as the result of the appulse.