PORTION OF THE COSMOS. AEROLITES. 429 



bers in a given interval of time. This brings us to the much 

 contested problem of the distinction between an extraordi- 

 nary and an ordinary fall of shooting stars. Two excellent 

 observers, Olbers and Quetelet, have respectively assigned, 

 the one 5 or 6, and the other 8, as the mean or average 

 hourly number of meteors visible within one person's sphere 

 of vision ( 695 ) on days not extraordinary. The discussion of 

 a very large number of observations is required for the elu- 

 cidation of this question, which is as important as the deter- 

 mination of the laws in respect to their direction. I there- 

 fore addressed myself with confidence to the already 

 mentioned observer, Julius Schmidt, at Bonn, who, long 

 accustomed to astronomical accuracy, has also comprehended 

 in his labours, with the animated zeal which belongs to him, 

 the whole of the phenomenon of meteors, of which the for- 

 mation of aerolites and their precipitation or fall upon the 

 surface of the Earth are regarded by him as only one of the 

 phases, the rarest, and therefore not the most important. 

 The following are the principal results contained in the 

 communications with which, in compliance with my request, 

 he has favoured me ( 696 ). 



" Between three and eight years of observation have given 

 for the phenomenon of sporadic shooting stars the mean 

 number of from 4 to 5 per hour : this is the ordinary state, 

 as distinguished from a periodical phenomenon. Ths 

 mean numbers of sporadically shooting or falling stars per 

 hour, in the several months, are as follows : 



January, 3 '4; February, ; March, 4'9; April, 2*4; 

 May, 3'9; June, 5'3 ; July, 4'5; August, 5*3; Sep- 



