302 
EASTMAN. 
between the observer and a star without diminishing the 
apparent brightness of the star or changing its position. 
While observing Comet I, 1866, in January, 1866, I saw 
on one occasion the nucleus of the comet pass directly over 
a star of the 9.2 magnitude with no more effect on the bright¬ 
ness of the star than would be produced by the close prox¬ 
imity of any object as bright as the comet’s nucleus. Similar 
accounts have been given by other observers, and the phe¬ 
nomenon is too well attested to admit of a reasonable doubt. 
The light from a star could not pass unobstructed through 
a solid body or a dense aggregation of solid bodies; and, 
considering this phenomenon alone or in connection with 
the appearance of the nucleus as it approaches and recedes 
from perihelion, it appears that we are driven to the conclu¬ 
sion that the nucleus of a comet is composed principally, if 
not entirely, of gaseous matter, which varies in form and in 
density from the effect of the sun’s attraction and repulsion. 
Comets and Meteors. 
The elements of the orbits of four meteor streams have 
been determined with considerable accuracy. These are the 
streams that produce the showers of November 13-14, No¬ 
vember 27, April 20, and August 10. 
It has also been found that the orbit of the meteor stream 
of November 13-14 coincides very closely with the orbit of 
Comet I, 1866. The orbit of the November 27 stream corre¬ 
sponds to that of Biela’s comet, the orbit of the April stream 
to that of comet I, 1861, and the orbit of the August stream 
is nearly identical with that of Comet III, 1862. 
The identify of these orbits is quite as good as could be 
expected from the uncertain character of the observations 
on which the adopted positions of the meteor streams depend. 
On these coincidences in the orbits of meteor streams and 
of certain comets depends principally the modern theory 
of comets and meteors, which, briefly stated, is as follows : 
Sporadic meteors, individual members of meteoric showers, 
