248 



ANNUAL REPORT SMITHSONIAN INSTITUTION, 195 7 



values, as seen in figure 5. Approximately 10 percent of the sporadic 

 and shower meteors have negative values of ZT, indicating the possi- 

 bility, but not the certainty, that they may be of asteroidal origin. 

 Orbital inclination is highly correlated with K in the sense that small 

 values of K are associated with orbits of low inclination. Figures 6 

 and 7 show the orbits of some meteors, both sporadic and in streams, 

 as determined photographically at Harvard. 



Meteors 

 Comets 

 Asteroids 



-1.0 



-.8 



+.8 +1.0 



FREQUENCY OF K CRITERION 

 Figure 5.— The frequency of the criterion K among meteors, comets, and asteroids. 



Although 21 meteor streams could be recognized from the first 144 

 photographic meteors, only 15 streams in all are yet certainly identi- 

 fied with individual comets. Only a few of these identifications have 

 been made photographically. Twelve streams and their definite iden- 

 tifications with comets are indicated in table 1. The extensive discus- 

 sion of comets, orbits, and meteor streams by Porter (1952) is highly 

 recommended to those who are interested in the details of these 

 relationships. 



Perhaps the most interesting of these associations is that between 

 the Taurid meteors of October and November and Encke's comet, 

 the comet of shortest period, 3.3 years. The individual meteoric 

 bodies in this stream are so widely distributed about the orbit of 

 Comet Encke that the meteors can be seen to enter the earth's at- 

 mosphere from two moving radiants, one below the plane of the 

 earth's orbit and one above it. Gravitational disturbances, or pertur- 

 bations, by Jupiter have so distributed the orientation of the various 

 orbits that an extraordinarily large volume of space is filled by par- 

 ticles that have been ejected from Comet Encke. Figure 8 shows the 

 orbital shapes for both Encke's comet and the Taurid meteors. 

 Whipple and Hamid (1951) have shown that some of these particles 



