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Published online by Cambridge University Press: 14 August 2015
The recognition of the astronomical origin of meteors is intimately connected to the Leonid meteors, and their tendency to “storm” with a period of 33 years. It was the Leonid storm of 1799, observed by Alexander von Humboldt among others, that first established the geographical extent of the phenomenon, with observations reported over 90 degrees of longitude and 60 degrees of latitude. During the 1833 storm, Olmsted (1834) at Yale and Twining (1834) at West Point established the radiant point in Leo, and the cosmic origin was clinched when H. A. Newton (1863), also at Yale, determined that the cycle repeated in intervals of sidereal years, not tropical years. Inspired by the 1866 storm, Adams (1866), Schiaparelli (1867), and Le Verrier (1867) determined a 33.25 year period and other orbital elements for the meteor stream; two years after the discovery of Comet Tempel-Tuttle in 1865, that comet was recognized as the parent body of the Leonid stream after von Oppolzer (1867) calculated a period of 33.17 years for the comet. Astronomers confidently predicted another storm in 1899, but none appeared, though there were good showers in 1901-1903. The years 1930-32 also brought fairly good showers, but 1966 brought the strongest storm witnessed in modern times, with an estimated 100,000 meteors per hour. Steady progress was made in meteor studies in the 20th century, especially with new photographic and radar techniques. The current question is what will happen in the 1997-1999 period; the only certainty is that the event will be studied with an even wider array of techniques.