1838.] Mr. Olmsled on the Meteoric Shoivers of Nov. 1836. 165 



Does not the recurrence of this phenomenon for six successive years, 

 2itthQ same period of the year, plainly shew its connection with the 

 progress of the earth in its orbit? and does not the fact, that the 

 greatest display occurs every where in places differing widely in 

 longitude at the same hour of the day, as plainly indicate its connec- 

 tion with the motion of the earth on its axis? The supposition of a 

 body in space, consisting of an immense collection of meteors stretch- 

 ing across the earth's orbit obliquely, so that the earth passes under 

 it in its annual progress, while places on its surface lying westward of 

 each other are successively brought, by the diurnal revolution, to the 

 point of nearest approach, will satisfy both these conditions. I can 

 think of no other that will. The " point of nearest approach" may 

 be merely the extremity, or the skirt of the nebulous body ; while the 

 greatest part of it, and, consequently, its centre of gravity, lies too 

 distant from the earth to be much influenced by its gravity. It would 

 not be at all inconsistent with the known extent of astronomical bodies, 

 to give to the body in question a breadth of thousands, and a length of 

 millions of miles. It was an accidental observation, made after the 

 conclusion was formed, which ascribes the origin of meteoric showers 

 to a revolving nebulous body, that first led me to suspect the zodiacal 

 light to be the body in question. This, according to Laplace, is such 

 a nebulous body, revolving round the sun in the plane of the solar 

 equator.* 



We actually observe it to reach over the orbit of the earth, making 

 an angle with its plane of only seven and a quarter degrees. It is not 

 difficult to place it in such a situation, that the earth shall come very 

 near to the skirts of it at least. We should, indeed, expect this meet, 

 ing of the two bodies to take place at the nodes of the solar equator 

 and therefore in December and June instead of November and April. 

 It is easily conceivable, however, that the aphelion of the zodiacal 

 light, at which place it approaches nearest to the earth, does not lie 

 exactly at the node, but so far from it that the earth passes it a month 

 before it comes to its node, at which time, moreover, the earth is more 

 than a million of miles nearer to the sun than its mean distance. In 

 endeavouring to fix the periodic time of the meteoric body, since it 

 must be either a year or half a year (for no other periodic time could 



* Mec. Celeste (Bowditch)-, vol. ii. 0^5, 



