SHOWERS OF SHOOTING STARS. 237 



of a thirty-three year period in the occasional recurrence 

 of grand shooting -star showers. The chief qualifications 

 of this statement would be twofold. In the first place, 

 the interval has been occasionally thirty-four years. In 

 the second place, it sometimes happens that at the return 

 of the thirty-three year period the passage of the meteors 

 makes no visible display, two consecutive years are 

 rendered memorable by great showers. At present this 

 particular shower occurs about the 15th November ; but 

 in earlier ages we find the date to shift slowly towards 

 the commencement of the year. Thus the display which 

 took place in A.D. 1698 was on the 9th of November ; while, 

 looking back still farther to one of the very earliest records, 

 viz., that of the year 934, we find the date has receded to 

 October 14th. This change of the day on which the 

 shower occurs is of profound theoretical importance in con- 

 nection with the discovery of the orbit which these meteors 

 pursue. The advance of the date IB, however, so slow that 

 for the past few generations as well as for the next, we may 

 sufficiently define this particular shower by the meteors 

 which enliven the skies between the 14th and the 16th of 

 November. In fact, the poetaster has parodied the well- 

 known lines for the days of the month by a similar effort, 

 which will serve to remind us also of another periodic shower 

 of shooting stars which occurs in August. He writes : 



" If you November's stars would see, 

 About the fifteenth watching be. 

 In August too stars shine from heaven, 

 On nights between nine and eleven." 



These lines are intended to imply that the day named 

 will usually bring, in every November, a few meteors at 



