On Meteorites. 105 
evident that they belong to a swarm which, after a revolution of 
thirty-three years around the sun, returns to the orbit of our globe. 
The comets are apparently something entirely different from the 
shooting-stars ; for while the latter are quite small and only appear 
within the terrestrial atmosphere, the comets are bodies of immensely 
greater size,comparatively speak- oh oN 
ing, and moving at a very great Ncs ce we SEE NG ANA ve 
‘distance from our little planet. 7 SE A 3 D w Ler 
Investigation shows, however, Wee fe WEA = 
that the orbits of both comets Y % | ae Maana d 
and shooting-stars have the same HENG f = ach r 
form, they being elongated conic } aan ben — A 
sections: hence their approaching ` SA 
from distant dark regions of 
space—now close to the sun, now 
again retiring to an immense 
distance from it. In regard to 3 
‘one comet, it has, furthermore, 
been ascertained that it moves in 
the same orbit as the swarm of 
shooting-stars mentioned above. fant. ‘Magnified 13 pip ghee i the 
The exact nature of the comets 7*9" 
has not yet been made out with any certainty, the best-sup- 
ported hypothesis being that they consist of immense quan- 
tities of small solid bodies. The comets nearest to the sun, when 
tn their greatest proximity to that body, are exposed to an enor- 
mous heat, soon followed, as they retire, by a cooling off equally 
enormous. The strong influence of the sun’s vicinity on the comets 
shows itself, among thes things, in the well-known long tail, which 
they project on the further side from the sun, and Bur nature and 
origin of which is still rather mysterious. Neither is the true 
nature of the shooting-stars fully ascertained. Many of them, 
however, appear to be small solid bodies rushing through the air ; 
and there are a great many intermediate forms between the common 
shooting-stars and the big fire-balls which explode with a thunder- 
like report and emit meteoric stones. ! 
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Fi, 
1 Mr. Sophus Tromholt, the author of the beautiful work, Under the 
Rays of Aurora Borealis, has sent me the following interesting 
or of a shooting-star :— 
One starlight but moonless Saturday night during November or 
