Meteoric Shower of 1936. 393 
stretching across the earth’s orbit obliquely,so that the earth passes un- 
der 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 form= 
ed, which ascribes the origin of the 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 La Place, is such a nebu- 
lous body, revolving around 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 74 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 meeting of the 
two bodies to take place at the nodes of the solar equator, and there- 
fore 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 en- 
deavoring to fix the periodic time of the meteoric body, since it must 
be either a year or half a year, (for no other periodic times could 
bring the two bodies together at intervals of a year,t) several con- 
siderations induced the belief, that half a year was the true period— 
an inference drawn especially from the apparent great excess of ve- 
locity of the earth at the point of concourse; but the period of a 
year, (or more probably, a little less than a year,) by implying that 
the two bodies are always comparatively near to each other, would 
better explain the occurrence of shooting stars at all seasons of the 
year, and would be particularly favorable to the explanation of those 
* Mec. Celeste, (Bowditch,) Vol. IT. 525. 
+ See Vol. XXVI. p. 166, of this Journal. 
Vou. SAA HNO, 2. 50 
