422 H. A. Newton— Biela Meteors of Nov. 21th, 1885. 



near 90° distant from where the shower happened would give 

 a stream of meteors nearly equal in thickness to the radius of 

 the earth's orbit into twice the limiting angle of the inclina- 

 tions of the individual orbits to the mean orbit. 



Unless therefore there is a nodal region for the several orbits 

 near tbe ecliptic the area B/ must have a breadth not much 

 greater than 3 /# 7, and consequently R a breadth not much 

 greater than 6' or 8' in a northerly and southerly direction. 



Again if the meteoroid orbits are nearly co-p'anar, and we 

 compare two orbits corresponding to two points at tbe extremi- 

 ties of the narrow area R/, it is easily seen that the tangents to 

 these two orbits make an angle with each other equal to the 

 length of R/. Now if two equal elliptic orbits of great eccen- 

 tricity and a common focus cut each other at a small angle 

 near perihelion the lines of apsides of the two orbits make an 

 angle with each other, nearly twice that made by the orbits 

 themselves at their intersection. Hence the major axes of the 

 two orbits corresponding to the two extremities of R' make an 

 angle with each other nearly double the length of R', that is, 

 nearly the length of R. That is, if R is several degrees long 

 E. and W., the lines of apsides of the meteoroid orbits are dis- 

 tributed over several degrees. The group itself therefore must 

 have enormous extent nearly in the mean plane, especially at 

 aphelion. This would be true even if we suppose that the 

 orbits have a nodal point at the place where they cut the 

 ecliptic. Such scattering seems inconsistent with present com- 

 pactness of the group, and a common history. 



That there should be nodal points, either of inclination of 

 planes or of intersection of orbits, where the earth cuts the 

 meteoroid stream might be supposed possible if we had but 

 one meteor-swarm to consider. But the same hypotheses must 

 be for like reasons extended to the Leonids, and Lyraids, and 

 perhaps to the Perseids. Unless the earth has been the con- 

 trolling body in the history of all these swarms such hypotheses 

 are violently improbable. 



The more reasonable explanation therefore of the large area 

 of radiation of the meteors of the Biela and other star-showers 

 is the glancing of meteors on entering the air. The burning 

 off of the angles of the solid fragments as soon as burning 

 begins makes them move in straight lines thereafter. The 

 curvature of path otherwise should continue through the whole 

 length of the luminous tracks. 



This glancing is not confined to the Biela meteors. It was 

 true of the Leonids and still more of the Perseids. It is rea: 

 sonable to assume that it is true of all shooting stars. It is not 

 therefore as simple a matter as some have supposed to separate 

 meteors into groups, alloting them to different radi.-jnt points, 

 or to establish the persistency or change of such points. 



