24 



SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 66 



The rich streams of shooting-stars afford so much observational 

 material that their radiant points can generally be determined more 

 accurately than those of the fire balls, as the following examples may 

 show in which the average errors are shown : 



Location of Apparent Radiants 



Right Ascension Declination Maximum 



Leonids 150.1° (±0.3°) + 23.0° ( ± 0.2° ) November 14 



Perseids 44-0° + 56.9° August 1 1 



Lyrids 271.5° (±0.7°) + 33.4° (± 0.4°) April 20 



Andromedids 23.8° (±0.9°) + 44.0° ( ± 0.2° ) November 26-28 



Quadrantids 230.9° (± 0.7°) -|- 51.3° (± 0.4°) January 2 



Geminids 108.3° (±0.5°) -|- 33.6° (± 0.4°) December 10-12 



Orionids 89.7° (±0.5°) -f 15.6° (± 0.3°) October 10-16 



Orionids 91.5° (±0.3°) -f- 157° (± 0.3°) October 16-22 



Denning believes* that the activity of the Perseids should be 

 assumed to extend from July 11 to August 19 by reason of which 

 the radiant point should experience a change from 



a=ii.5°, 8 = 47-7° to a=56.6°, 8 = 59.1°. 



All these streams consist of more or less densely collected particles 

 along the whole extent of their paths as far as yet known, but only 

 the Leonids consist of a specially rich swarm returning to the peri- 

 helion in a well-established period of 33^ years. 



2. The Results as to the Altitude of the Luminosity and of 



THE Terminal Points and their Relations to 



Other of the Factors 



In this respect we must distinguish between the small phenomena 

 which we know as shooting-stars and the large meteors known as fire 

 balls which frequently exhibit during their path through the atmos- 

 phere a remarkable development of light and often produce great 

 noise and sometimes well-established falls of meteorites. 



With regard to the shooting-stars of the so-called Perseids in 

 August, Weiss,* in Vienna, from the discussion of 49 reliable corre- 

 sponding observations, found on the average for the first luminosity 

 115 km., for the extinction 88 km. 



Independent of this H. A. Newton ' also found for the Perseids 

 from 38 observations the following altitudes, viz. : luminosity 112 km. 

 and extinction 90 km. in excellent agreement with the preceding. 



' W. F. Denning, Astr. Nachr. 148 (1899), P- 283. 



' E. Weiss, Wien. Ber., 1868. 



' H. A. Newton, American Journal of Science and Arts, 2 Series, 40. 



