OBSERVATIONS OF LUMINOUS METEORS. 51 



the number of the cometary perihelia closest to the sun in the forward qua- 

 irants, relatively to the direction of his proper motion in space, is also re- 

 garded as indicating the direction of the sun's motion through the meteor- 

 ;loud in a manner which the facts of observation evidently corroborate. 



3. On the Periods of certain Meteoric rings. By Professor Kirkwood (read 

 ;o the American Philosophical Society, March 4, 1870).— According to the 

 iomputed elements of the Comet I. 1861 (by Oppolzer), first shown by Dr. 

 Edmund Weiss (Astron. Kachr. no. 1632) to agree very closely with those of 

 he April meteor-stream, its periodic time of revolution is 415-4 years. On 

 he other hand, Professor Kirkwood points out that, without accepting a shorter 

 )eriodic time of revolution, the former April displays recorded in ancient 

 imes do not agree with the time of revolution of the comet. Adopting a 

 )eriod of about 28^ years for the cycle of returns of the April shower, the 

 vhole of the dates of its appearance selected by Professor ll^ewton as agre'eing 

 veil with those of its most recent appearance in the present century are re- 

 iresented with perfect accuracy by the following scheme : — 



Dates of former appearances. Interval in years. 



'>om B.C. 687 to B.C. 15 672-000=24 periods of 28-000 years each. 



B.C. IS to A.D. 582 597-000 = 21 „ 28-429 



A.D. 582 to A.D. 1093-714 (between] 



1093 and 1096) jSii7i4=i» „ 28-429 „ 



A.D. 1093-714 to 1222-143 28-429:^1 „ 28-429 



A.D. 1222-143 to 1803 680-857=24 „ 28-369 „ 



The periodical time of 28^ years corresponds to an ellipse whose major 

 xis is 18-59, and whose aphelion distance is very nearly equal to the mean 

 listance of the planet Uranus. A remark of Mr. Du Chaillu is here believed 

 to be rightly recalled, that he observed the April meteors in the equatorial 

 parts of Africa almost as brilliant, and leaving streaks more enduring than 

 those of the great November meteor-shower (of which he was also an ob- 

 server in England, in the year 1866). If the date of Mr. Du ChaiUu's obser- 

 vation was about the year 1860, a corroboration of Professor Kirkwood'a 

 cycle of 28^ years repeated twice since the great display of those meteors in 

 the year 1803 would be thence derived. The April meteor-shower was also 

 sufficiently bright in the year 1863 to make its approach to an epoch of 

 maximum brilliancy in about that year a somewhat probable conjecture. 



Among the formerly recorded star-showers which appear to have certainly 

 been connected with the December meteor-system. Professor Kirkwood points 

 out a notice of such an occurrence in the year a.d. 901. Others are found 

 to have taken place in the years 930, 1571, 1830, 1833, and 1836, with an 

 apparent maximum in the year 1833, when as many as ten meteors were 

 seen simultaneously. Finally, pretty abundant displavs of the shower were 

 observed in the years 1861, 1862, and 1863, with a jprobable maximum in 

 the year 1862. These dates indicate a period of about 29^ years, thus^ 



901 to 930 I period of 29000 years. 



930 to 1571 22 „ 29136 „ 



1571 to 1833 9 „ jg-iii ,, 



1833 to 1862 1 „ 29-000 „ 



A third meteoric shower, that of the 15th-21st of October, presents, again, 

 a similar period of revolution. The recorded dates of apparitions which cor- 

 respond m the times of their appearance with the present meteor-showers of 

 the 15th-21st of October are the years a.d. 288, 1436 and 1439, 1743, and 

 1798, on each of which occasions a great number of shooting-stars were 



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