296 METEORS AND AEROLITES. 



its orbit without precipitation of its contents ? Taking the 

 question generally, we incline at once to answer in the affir- 

 mative. It must be admitted that stones have sometimes 

 fallen from what seems to be a clear heaven ; or with no other 

 appearance than that of a small circular cloud suddenly 

 forming in the sky. But these, as far as we know, are 

 events of the daytime; and what is seen as a dark form 

 under the light of the sun may appear a fiery globe in the 

 darkness of night. If it be well proved in a few cases that 

 these fire-balls exploding have thrown down stones upon the 

 earth, the presumption becomes strong that analogous mete- 

 orical elements are present in all, whether precipitated or 

 not. M. Saigey does not fully admit the relation of bolides 

 and aerolites ; but we believe the argument fairly to stand 

 as we have stated it. 



The subject of Shooting-Stars (etoiles filantes) separates 

 itself somewhat farther from the phenomena already de- 

 scribed, though still manifestly connected in various ways. 

 The more important peculiarities here are the smaller size 

 of these meteors ; their infinitely greater frequency ; the arcs 

 they describe ; their frequent occurrence in showers ; and the 

 observed periodicity in certain of these latter occurrences. 

 The difference of magnitude is the least important of their 

 characters ; since we find every gradation of size, from the 

 shooting scintilla of light to globes large as the moon. 

 Those gradations, partially visible to any eye gazing into the 

 depths of the sky on a clear night, are especially seen during 

 the showers of stars just adverted to. The periodicity of 

 some of these showers is the point of greatest interest in the 

 enquiry ; a research still very imperfect, but which time is 

 certain to complete, and probably at no distant period. 



The common aspect of shooting-stars needs no description. 

 It was one of the earliest objects of science as directed to 

 them, to determine their heights, duration, and velocity ; and 



