200 THE BORDERLAND OF SCIENCE. 



It will be remembered that a part of the evidence 

 respecting meteorites was based on the actual analysis, 

 chemical and microscopical, of masses which have fallen 

 upon the earth from interplanetary spaces. Shooting- 

 stars do not fall as masses ; and though their nature 

 may be to some extent inferred from the spectroscopic 

 analysis of their light, as well as from the conside- 

 ration of the quantity of light which they emit, we are 

 unable to apply to them the reasoning which had chief 

 weight in the case of meteorites. We cannot assert 

 that the substance of shooting-stars came originally 

 from some star or sun in space, on the strength either 

 of the molecular structure of those bodies or of their 

 chemical condition, for we know absolutely nothing on 

 either point. A shooting-star may, for aught that is 

 known, contain, like meteoric iron, an excess of 

 occluded hydrogen; or, when it first reaches our 

 atmosphere, it may have that peculiar microscopical 

 structure which has led Mr. Sorby to regard certain 

 meteorites as expelled from glowing orbs like our sun 

 and his fellow suns ; but we have no means of ascer- 

 taining whether either condition prevails. 



There are certain circumstances, however, about 

 such meteor systems as the Leonides, Perseides, and 

 these Bielan shooting-stars, which have a very decided 

 bearing on the question of their origin. 



If a meteoric mass were expelled from the sun it 

 would return to the sun, unless either it encountered 

 one of the planets, or else had been expelled with a 

 velocity great enough to carry it for ever away from 



