404. THE BEAUTIES OF NATURE CHAP. 
by the Sun, the tail, how or why we know 
not, is repelled. When once driven off, more-— 
over, the attraction of the Comet is not suf- 
ficient to recall it, and hence perhaps so many 
Comets have now no tails. 
Donati's Comet, the great Comet of 1858, 
was first noticed on the 2d June as a faint 
nebulous spot. For three months it remained 
quite inconspicuous, and even at the end of 
August was scarcely visible to the naked eye. 
In September it grew rapidly, and by the 
middle of October the tail extended no less 
than 40 degrees, after which it gradually 
disappeared. 
Faint as is the light emitted by Comets, 
it is yet their own, and spectrum analysis has 
detected the presence in them of carbon, 
hydrogen, nitrogen, sodium, and probably of 
iron. 
Comets then remain as wonderful, and 
almost as mysterious, as ever, but we need no 
longer regard “a comet as a sign of impend- 
ing calamity; we may rather look upon it as 
an interesting and a beautiful visitor, which 
comes to please us and to instruct us, but 
