Page:The Scientific Monthly vol. 3.djvu/549

 WHAT WE KNOW ABOUT COMETS 543

was essentially identical with the orbit of Comet 1862III. Here are the elements of the two orbits.

Meteora of August Orbits of 9. 10. 11 Comet 1M2III

Perihelion passage July 23.62 August 22.9

Longitude of perihelion 343° 38' 344** 41'

Ascending node 138 16 137 27

Inclination 63 3 66 25

Perihelion distance 0.9643 0.9626

Period of revolution 105 years? 123.4

Direction of motion retrograde retrograde

The difference in the two perihelion times does not mean that their orbits were different even to the minutest degree, but only that, moving on the same orbit, they reached the point nearest the sun at slightly different times ; that is, one of the bodies traveled over the orbit a little in advance of the other. The revolution period assigned to the meteors is subject to considerable error because it is not possible to observe the paths of the meteors with great accuracy.

There were rich and startling showers of meteors on November 12, 1799, and on November 12-13, 1833. H. A. Newton examined the literature of meteoric falls and found that many similar showers had been observed at intervals of thirty-three years running back several centuries, to 902 a.d., *'the year of the stars,'^ and he confidently predicted that another great shower would occur on November 13-14, 1866. His prediction was abundantly verified. Early in 1867 Schia- parelli and Le Verrier independently computed the orbit of these meteors, and Schiaparelli and Oppolzer independently found it iden- tical with the orbit of the comet 18661. Here are the elements of the two orbits :

Meteors of Novem- Orbits of ber 18 Comet 18661

Perihelion passage November 10.092 January 11.160

Longitude of perihelion 56^ 25'.9 60** 28'.0

Ascending node 231 28 .2 231 26 .1

Inclination 17 44 .5 17 18 .1

Perihelion distance 0.9873 0.9765

Eccentricity 0.9046 0.9054

Semi-major axis 10.340 10.324

Period of revolution 33.250 years 33.176 years

Direction of motion retrograde retrograde

It is impossible to doubt that these November meteors and the comet referred to were traveling in the same orbit.

The so-called Lyra meteors are visible about April 20 each year. It was noticed in 1867 by Weiss that the orbit of the Lyra meteors is essentially identical with that of the comet 18611.

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