270 ON THE ORBIT OF THE NOVEMBER METEORS. [34 



From these data Professor Newton infers that these displays recur in 

 cycles of 3 3 "2 5 years, and that during a period of two or three years at 

 the end of each cycle a meteoric shower may be expected. He concludes 

 that the most natural explanation of these phenomena is, that the November 

 Meteors belong to a system of small bodies describing an elliptic orbit about 

 the Sun, and extending in the form of a stream along an arc of that 

 orbit which is of such a length that the whole stream occupies about 

 one-tenth or one-fifteenth of the periodic time in passing any particular 

 point. He shews that in one year the group must describe either 



2 33-25' r l &25' r 33-25 



revolutions, or, in other words, that the periodic time must be either ISO'O 

 days, 185'4 days, 354'6 days, 376'6 days, or 33 - 25 years. 



It is seen that the time of the year at which the meteoric shower 

 takes place becomes gradually later and later, and that accordingly the 

 Earth's longitude at that time, or the longitude of the node of the orbit 

 of the meteors, is gradually increasing. Professor Newton finds that the 

 node has a mean motion of 102 //- 6 annually with respect to the Equinox, 

 or of 52"'4 with respect to the fixed stars ; and he remarks that since 

 the periodic time is limited to five possible values, each capable of an 

 accurate determination, and since therefore from the position of the radiant 

 point the other elements of the orbit can be found, it seems possible to 

 compute the secular motion of the node for each periodic time with con- 

 siderable accuracy, and the actual motion of the node being known, we 

 have thus an apparently simple method of deciding which of the five periods 

 is the correct one. 



Soon after the remarkable display of these meteors in November last, 

 I undertook the examination of this question. From the position of the 

 radiant point as observed by myself, I calculated the elements of the orbit 

 of the meteors, starting with the supposition that the periodic time was 

 35 4 - 6 days, the value which Professor Newton considered to be the most 

 probable one. The orbit which corresponds to this period is very nearly 

 circular, and it readily follows from the ordinary theory that the action 

 of Venus would produce an annual increase of about 5" in the longitude 

 of the node, and that of Jupiter an annual increase of about 6". The 

 calculation of the motion of the node due to the Earth's action, presented 

 greater difficulty in consequence of the two orbits nearly intersecting each 

 other. I succeeded, however, in obtaining an approximate solution, applicable 



