SHOOTING STARS. 213 



" The mean number of sporadic shooting stars appearing 

 there has been found, from many years of observation (be- 

 tween 3 and 8 years), a fall of from four to Jive 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, on the 

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

 that of August, the stream of Laurentius presented the follow- 

 ing gradual increases from sporadic to periodic, upon an av- 

 erage of from three to eight years of observation. 



Number of TM,,mhpr 



rrr ~ 



6th of August 6 1 



7th " 11 3 



8th " 15 4 



9th " 29 8 



10th " 31 6 



llth " 19 .-.5 



12th " 7 3 



The last year gave for the hour, notwithstanding the clear 

 moonlight : 



On the 7th of August 3 Meteors. 



8th " 8 



9th ' 16 



10th. " 18 



llth " - 3 



12th " 1 Meteoi. 



(According to Heis, there were observed on the 10th of Au- 

 gust : 



1839, in one hour, 160 Meteors. 



1841 "'. 43 



1841 " 50 



In the August meteor-stream in 1842, there fell at the time 

 of the maximum, in ten minutes, 34 shooting stars.) % All 

 these numbers refer to the circle of vision of one observer. 

 Since the year 1838, the November falls have been less brill- 

 iant. (On the 12th of November, 1839, Heis still counted 

 hourly 22 to 35 meteors ; likewise, on the 13th of Novem- 



