Prof. Olmsted on the Zodiacal Light. 321 



that of the zodiacal light, a period as short as one third of a year, 

 or even less. 



I do not assert positively that the zodiacal light is the veritable 

 body which produces the meteoric showers of November and Au- 

 gust. Before such an hypothesis can be proved to be true or 

 false, with certainty, a greater number of precise observations 

 continued through a series of years, would require to be made, 

 and a careful comparison instituted between the hypothesis and 

 the facts. Should the zodiacal light be found- at last incompe- 

 tent to explain the periodical meteors, the existence of a nebu- 

 lous body, as inferred from a full survey of the facts in the case 

 of the meteoric shower of November 13thj 1833, independently 

 of all hypothesis, will still be true. But, with great deference, 

 I submit to the Association, the following presumptions in favor 

 of the opinion that the zodiacal light is the nebulous body which 

 produces the meteoric showers of November. 



1. The zodiacal light, as we have found in our inquiry into 

 Its nature and constitution, is a nebulous body. 



2. It has a revolution around the sim. 



3. It reaches beyond and lies over the earth^s orhit^ at the time 

 of the November meteors^ and makes but a small angle with the 

 ecliptic. 



4. Like the '^ nebulous body," its periodic time is commensnr- 

 ahle with that of the earth, so as to perform a certain whole num- 

 her of revolutions while the earth performs one, and thus to com- 

 plete the cycle in one year, at the end of which the zodiacal light 

 and the earth return to the same relative position in space. This 

 necessarily follows from the fact that at the same season of the 

 year it occupies the same position one year with another, and 

 the same now as when Cassini made his observations nearly one 

 hundred and sev^enty years ago.* 



5. In the meteoric showers of November, the meteors ore 

 (actually seen to cowe from the extreme portions of the zodiacal 

 lights or rather a little beyond the visible portions; and the same 

 ^'as true of the radiant point of the meteors, (when watched, 

 as it was by Mr. Fitch,t from Oct. 16th to Nov. 13th, 1837,) 

 namely, that the radiant always keeps the same relative position 

 with respect to the vertex of the zodiacal light, being with that 

 vertex in Gemini, in the month of October, and travelling along 

 with it through the Constellation Cancer, and into Leo, where it 

 was on the morning of the meteoric shower. Observations, so 

 far as they have been made, indicate a similar relation between 

 the meteors of August and the extreme portions of the zodiacal 

 lisht. 



For the first sui^gestion of this aiialogj, I am indebted to one of my former 

 P^PiU, Mr. Hubert jS'ewton. 

 T Amer. Jour, ScL, xxxiii, 3S6. 



