108 



RESEARCHES CONCERNING THE PERIODICAL 



must suppose a compensation of their discrepancies throughout the two dis- 

 plays, an event the more improbable as the aggregate of the concurrent events 

 of 1837 and 1839 is increased. These events amount in all to five hundred 

 and thirty-six on these two occasions. When we add to these fifty-six concur- 

 rent results in 1840, and recollect that the number of events, confirmatory in 

 their general character, and amounting to some thousands, as recorded in the 

 observations at various stations in Europe and America in the years 1836 — 

 1840, about the 10th of August, the only legitimate conclusion is that these 

 anniversary flocks of shooting stars are moving in the same part of the same 

 orbit, round some central body. I have already shown that this central bodij 

 can be no other than the sun. As there is no good reason for the contrary, I 

 am led to extend the same general conclusion to the respective August anni- 

 versaries enumerated in Table V., and to suppose the tenth or twentieth part 

 of the single meteors seen on those occasions which were unconformable, to 

 have composed the ordinary promiscuous or sporadic meteors seen throughout 

 the year. In such a case, these periodical phenomena, as Prof Erman" 

 remarks, can only be explained by one of two hypotheses — either that the 

 successive displays are parts of the same group or cluster, with a half yearly 

 or yearly period, or that there exists in the particular part of the system 

 which has for its radius vector 1.013, and its heliocentric longitude 137° — 

 139°, without any latitude, a continuous succession of these bodies at all 

 seasons of the year, moving always in the same orbit, though only encoun- 

 tered annually by the earth. It is obvious that the latter supposition of con- 

 tinuity of succession of these moving bodies at the same point of space, and in 

 the same direction, requires the farther hypothesis of their forming a part of a 

 conic-sectional ring, or lens, having the sun in its focus. In this case the 

 anniversary display must continue to be witnessed while the radius vector, and 

 anomaly of the node, remain the same, or while their periodical fluctuations 

 are less than the breadth of the ring. When they exceed this breadth, the 

 phenomenon ceases to recur, till, in the course of time, the node returns to the 

 same anomaly and corresponding radius vector. 



7. The remaining remarkable showers of meteors in the catalogue, may be 

 accounted for by supposing the earth, at the successive dates, to have encoun. 



«* Astr. Nachr., Nos. 385 and 390. 



