144 ASTRONOMY FOR 1889, 1890. 



plaiiatiou of meteors are given, and extensive catalogues of observed 

 meteors and meteorites. 



Mr. IJenning- pointed out several years ago that there were a number 

 of meteor streams in which the meteors seemed to radiate from the same 

 point m the sky for a period of three mouths or more. The only expla- 

 nation of this phenomenon seemed to be that the meteors were moving 

 with frightful velocity through space, but M. Tisserand, froui a mathe- 

 matical study of the problem, shows that these meteors do not all 

 come from the same stream ; they may perhaps belong to a family i)re- 

 senting certain common characteristics, but they are in reality ditferent 

 strsams accidentally falling together, a not very improbable assumption 

 considering the great number of meteor streams and the difficulty of 

 determining the radiant with any degree of precision. 



Mr. Denning does not, however, admit that an accidental coincidence 

 of radiant points of dilferent streams is a sufficient explanation of the 

 phenomena he has observed. 



The zodiacal light. — Prof. Arthur Searle, who has made a special 

 study of the zodiacal light, finds that the permanence of the ordinary 

 western light, subject only to slight variations in the degree of visi- 

 bility, iscontirmed by the observations of the last 50 years at the Hanaud 

 Observatory. The zodiacal bands, which are said to form a prolong- 

 ation of the ordinary zodiacal light, were not seen, though stellar or 

 nebulous bands, one extending from Aquila to the Pleiades, and the 

 second from Prtesepe to Coma Berenices have been noticed and perhaps 

 offer an explanation of the zodiacal bands. The Gegenschein, it is sug- 

 gested, may be due to a maximum of light reflected from the meteoric 

 matter scattered in the solar systeu). 



The observations of Prof. C. Michi Smith, carried on at intervals 

 since 1875 indicate a periodic appearance of the line at wave-length 556 

 in the zodiacal light spectrum ; a lineditfering but little in wave-length 

 from the auroral Hue (wavelength 550,7). 



PLANETS. 



A very laborious work is being carrie<l on in the otBce of the Ameri- 

 can Ephemeris, under the superintendence of Professor Newcomb — the 

 redeterminati(tu of the elements of all the larger i)lanets. Professor 

 Newcomb's plan includes the re-reduction of the older planetary obser- 

 vations and the discussion of the later ones, with a view of reducing 

 them all to a uniform system. Another branch of this planetaiy work 

 is a determination of the mass of Jupiter from the motions of Poly- 

 hymnia, and a comparison of Hansen's tables of the moon with observed 

 occultatious since 1750. 



The first volume of this series of memoirs upon the theories of the 

 major planets has appeared in the "Astronomical Papers," of the 

 Ameiicau epliemeris, luuiig a new discussion ot Jui)iter and Saturn by 

 Hill. He has determined the complete aualytical expressions for the 



