PROGRESS OF METEORIC ASTRONOMY IN AMERICA. 281 
Of the theory of meteors, Mr. Herrick wrote: 
“ The most probable hypothesis is that there are revolving 
around the sun millions of small planetary and nebulous 
^bodies of various magnitudes and densities, and that when 
any of these dart through our atmosphere they become 
ignited and are seen as shooting-stars.” 
In discussing a paper on meteors by Prof. Erman (Schu¬ 
macher’s Ast. Nach. No. 385) Prof. Benjamin Peirce j after 
pointing out an error in Erman’s work, concludes in these 
words : “ The plane of the meteors cannot differ much from 
that of the ecliptic, and their relative velocity cannot exceed 
one-third of the earth’s velocity. A ring so nearly in the 
plane of the earth’s orbit must be subject to great perturba¬ 
tions ; and, if there is one, I think that no observations which 
we can make will enable us to calculate its motions with any 
degree of accuracy.” 
On January 15, 1841, Prof. S. C. Walker 1 2 read a paper 
before the American Philosophical Society, “ On the peri¬ 
odical meteors of August and November,” in which the fol¬ 
lowing points were discussed: 
The relative velocities of meteors; 
The relative directions of meteors in space; 
The periodical or anniversary display of meteors ; 
The respective plausibilities of the hypotheses of a single 
cluster with a half-yearly or yearly period, or that of a con¬ 
tinuous ring for the periodical meteors of August and No¬ 
vember ; 
The theories of aerolites and shooting-stars; 
The variation of the relative velocity and of the conver¬ 
gent point; 
And principally the investigation of formulae for com¬ 
puting the elliptic elements of the orbit of a meteor from its 
observed relative velocity and direction. 
In 1844 an “ Essay-on Solid Meteors and Meteoric Stones” 
1 Trans. Am. Phil. Soc., VIII 2 , 83. 
2 Trans. Am. Phil. Soc., VIII 2 , 87. 
