SHOOTING STAES. 577 



excellent observers, Olbers and Quetelet, have given as the 

 mean number of meteors which can be reckoned hourly in 

 the range of vision of one person upon not extraordinary days, 

 the former five to six, the latter eight meteors. 17 For the 

 discussion of this question, which is as important as the de- 

 termination of the laws of motion of shooting stars, in reference 

 to their direction, a great number of observations are required. 

 I have therefore referred with confidence to the already- 

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

 accustomed to astronomical accuracy, takes up with his 

 peculiar energy the whole phenomena of meteors of which the 

 formation of aerolites.and their fall to the Earth appear to him 

 merely a special phase, the rarest, and therefore not the most 

 important. The following are the principal results of the 

 communications which I requested from him. 18 



" The mean number of sporadic shooting stars appearing 

 there has been found from many years of observation (between 

 3 and 8 years), a fall of from 4 to 5 in the hour. This is the 

 ordinary condition when nothing periodic occurs. The mean 

 numbers of sporadic meteors in the individual months, give 



for the hour, January, 3'4 ; February, ; March, 4-9 ; April, 



2'4 ; May, 3'9 ; June, 5'3 ; July, 4*5; August, 5-3 ; September, 

 4-7 ; October, 4-5 ; November, 5-3 ; December, 4*0. 



" Of the periodic meteors there may be expected r , on the 

 average, in each hour, above 13 or 15. For a single period, 

 that of August, the stream of Laurentius presented the following 

 gradual increases from sporadic to periodic, upon an average 

 of from 3 to 8 years of observation. 



17 Cosmos, vol. i. p. 100. 



18 All that is marked in the text with inverted commas 

 I am indebted for to the friendly communication of Herrn 

 Julius Schmidt, attached to the observatory at Bonn. With 

 regard to his earlier works of 1844, see Saigey, p. 159. 



