90 Mr Olmsted on the Meteoric Showers 



indeed, expect this meeting 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, how- 

 ever, 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 bring the two bodies together at intervals of a year,*) seve- 

 ral considerations induced the belief, that half a year was the 

 true period, an inference drawn especially from the apparent 

 great excess of velocity 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 shoot- 

 ing stars at all seasons of the year, and would be particularly 

 favourable to the explanation of those meteoric showers which 

 have on two occasions at least,-f- occurred near the last of April, 

 a time distant about half a year from November, and therefore 

 sustaining a like relation to the opposite point of its orbit. In 

 such a case, meteoric showers would occur in April and Novem- 

 ber, for the same reason that the transits of Mercury take place 

 in May and November exclusively. The greater frequency of 

 meteors in November than in April, naturally results from the 

 greater proximity of the earth to the sun at the former than at 

 the latter period ; to which, perhaps, may be added the effect of 

 the eccentricity of the orbit of the meteoric body, the aphehon 

 being on the side of November. In the present state of our 

 knowledge on this subject, I regard it as a point open for in- 

 quiry, whether it will best accord with all the phenomena of 

 shooting stars, to give to the meteoric body a period of nearly 

 one year, or of half a year. 



* See vol. xxvi. p. 166, of this Journal. 



■f In Virginia, and various other parts of the United States, in 1803, and 

 in France in 1095, making suitable allowances for the more rapid progress of 

 the earth through the winter signs, and for the change of style, and the me- 

 teoric shower of the 20th of April 1095, occurred at very nearly the very op- 

 posite point of the earth's orbit. 



