38 Mr. H. A. Newton on certain recent 



at the least is not improbable. The reasonings of M. Schiaparelli, 

 which will be spoken of further on in this article, strengthen 

 this probability. 



But we meet with some difficulty in accepting the proposition 

 that a ring or stream may be of such breadth as to require eight 

 or ten weeks for the earth to traverse it — that is, that the ring 

 may extend 60° or 70° along the ecliptic ; or rather, if there 

 were so broad a ring or stream, it would not appear to have a 

 radiant area so small and so well marked as to be detected. 



The position of the radiant indicates that point of the heavens 

 from which the relative motion of the meteoroids with reference 

 to the earth is directed. This direction is the resultant of two 

 absolute motions — that of the meteoroids and that of the earth. 

 If either of these should change, the place of the radiant will 

 change. 



But during these eight or ten weeks the direction of the 

 earth's motion would change 60° or 70°. If the direction of 

 the meteoroids' motions were supposed parallel throughout the 

 breadth of the stream, yet this change in the direction of the 

 earth's motion alone appears to necessitate a change of the posi- 

 tion of the radiant by a distance on the heavens of not less than 

 30° or 40°. 



But for a group of such thickness we can hardly suppose the 

 absolute motionsof the meteoroids parallel throughout its breadth. 

 Each meteoroid must move about the sun in its own orbit ; and 

 though this is not entirely inconsistent with a parallelism of the 

 paths where the group crosses the ecliptic, yet such a case is ex- 

 tremely improbable. Again, it appears necessary that a meteo- 

 roid which is now on one side of the stream should be after half 

 a revolution on the opposite side. Hence we might reasonably 

 expect that at the centre of the stream we should find their 

 paths crossing each other at large angles, angles comparable 

 in magnitude to the 60° or 70° which measures on the ecliptic 

 the breadth of the stream. Such divergence of directions of the 

 individual members of the group would make the existence of an 

 apparent radiant of moderate area impossible. 



Again, a stream whose thickness is so great may be expected 

 to have also large breadth in direction of the radius-vector. 

 This again would make the parallelism of the paths, and conse- 

 quently the apparent radiation improbable. 



In fact a ring of such enormous thickness as to require two 

 months for the earth to cross it, would seem not only to lose all 

 the essential characteristics of a distinct group, but also to be 

 unable to manifest its existence by a constant and small radiant 

 area. 



The conclusions of Mr. Greg and Dr. Heis are derived almost 



