SECT. XXXVIf. SHOOTING STARS, 385 



to confirm him in this opinion. He agrees with La 

 Place in thinking that the zodiacal light is a nebulous 

 body, revolving in the plane of the solar equator. In 

 fact, this light stretches beyond the earth's orbit, making 

 an angle of about 74 with the plane of the ecliptic, and 

 according to observation, it is sometimes seen in the 

 dawn, and sometimes in the twilight, like an inferior 

 planet. It was seen by Professor Olmsted for several 

 weeks previous to the 13th of November, in the morn- 

 ing dawn, with an elongation (N. 231) of from 60 to 

 90 west of the sun. It then by degrees withdrew from 

 the morning sky, and appeared in the evenings imme- 

 diately after twilight, rising like a pyramid through the 

 constellations Capricornus and Aquarius, to an elonga- 

 tion of more than 90 eastward of the sun. A change 

 like this taking place annually about the 13th of Novem- 

 ber, has led the Professor to believe that it is to the 

 zodiacal light we are indebted for those splendid exhibi- 

 tions of falling stars which take place at that season. 



The orbit already described is that which he formerly 

 assigned to this nebulous or cometary body, but he is 

 now of opinion that it has a period of something less 

 than a year, which would not only account for the shoot- 

 ing stare of the 13th of November, but would also ac- 

 count for those that happen at all seasons, and for some 

 very great showers of them that have taken place on 

 two occasions near the end of April. In the position 

 assigned to this orbit by Professor Olmsted, showers of 

 shooting stars may happen in November and April. 

 Since the last edition of this book a very able memoir 

 has been published by M. Biot, in which that great 

 philosopher shows that in his opinion also, meteoric 

 showers are owing to the zodiacal light coming into pe- 

 riodic contact with the atmosphere of the earth. Which 

 of these conjectures may be nearest the truth time alone 

 can show ; but certain it is that the recurrence of this 

 phenomenon at the same season for seven successive 

 years proves that it can arise from no accidental cause. 

 25 KE 



