96 REPORT— 1864. 



Newton's list, wtich therefore affords wider average limits of height than 

 those given in the last Eeport. The results may be thus compared : — 



Average height at first 



appearance, No. of Observations, Reference. 



70-1 Brit. St. miles. 178 since Sept. 1798. B. A. Report, 1863. 



73-5 „ „ 234 „ „ Am. Journ. Sci., July 18G4. 



Average height at dis- 

 appearance, No. of Observations, Reference. 

 54-2 Brit. St. miles. 210 since Sept. 1798. B. A. Report, 1863. 

 50-6 „ „ 290 „ „ Am. Journ. Sci., July 1864. 



The mean height of luminous meteors at appearance is accordingly 72, and 

 at disappearance 52 British statute miles above the level of the sea, with a 

 probable error of only tiuo miles, 



IV. ' N'ovEMBER Star-showers,' by Professor Newton. 



(Am. Journ. Sci. vol. xxxvii. p. 377, and vol. xxxviii. p. 53.) 



Comparing together the dates of thirteen historic star-showers, from Oc- 

 tober 13th, 902, to November 13th, 1833, the existence of a common meteoric 

 shotver becomes apparent. The node of the ring has an annual ^»-o-cession of 

 l'-711 (reckoned from mean equinox), or of 52"-56 reckoned from a fixed 

 equinox along the ecliptic. By this amount the date of the return has been 

 delayed one day in every 34 years since the first appearance of the shower ; 

 and the narratives are in accordance with a single meteoric phenomenon, of 

 which the yearly period is 365-271 days, returning with especial intensity 

 four times in every 133 years. A want of punctuality of one, two, or even 

 three years in the return of the display may be accounted for by the revo- 

 lution of the earth on its axis, by which observers were deprived of a view 

 of the spectacle during a part of its existence. The explanation of the 

 periodicity depends, not iipon the perturbations of the eartli or of the ring, 

 but upon the true periodical time of revolution of the cloud. Its displace- 

 ment yI^ parts of a revolution from the node per annum may be accom- 

 panied with 0, 1, or 2 complete revolutions round the sun, but with no frac- 

 tional i^art of a revolution, because the cloud has been encountered at the 

 node with almost equal intensity on two successive years (1832 and 1833). 

 The displacement cannot be accompanied vrith any greater intee/ral number 

 of revolutions than two, on account of its distance from the sun. As, more- 

 over, the true motion of the November meteors is sensibly perpendicular to 

 a radius-vector from the sun, probability must be held to decide in favour 

 of the nearly circular orbit, with li-j-fi? revolution per annum, and with a 

 velocity nearly equal to that of the earth, but in a retrograde direction. The 

 inclination observed corresponds to nearly 17° with the echptic. 



Should more than one revolution be performed in one year by the meteoric 

 cloud, the two or three successive encounters which compose one principal 

 meteoric epoch must fall earlier in the year, and vice versa. Sufficient mate- 



