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SPECTRUM AND APPEARANCE OF THE RECENT COMET. 8&3 
that they have matter in an oxidizable shape, and it may 
be that the comets as they approach the sun find conditions 
existing which cause a violent chemical action on their surfaces. 
The subject is a difficult one, but whatever be the —_ cause 
we know that it is very energetic, because we can see effects 
from day to ey, and the changes going on take place on ie side 
nearest the 
I took io. sets of measures of the lines ae the evening of June 
6th ; for the first a low w power was used on the reading telescope, 
The means of these gave for A line the wave length 5580; 
for B, 513-5 ; for C, 467°3. A higher power was then used : the 
gave 512-4, By this time the comet had got so low that I could 
not see the line ©. The measures, considering the position of 
the comet, and the difficulty of getting them at all during the 
short time between daylight and the comet’s setting, are very 
satisfacto 
In the standard works of reference the information about 
cometary spectra is very meagre. I was magne very glad to 
receive in May a very valuable work on the spectra of comets, 
and similar carbon spectra, by Dr. B. Hasselberg, of “4 AGP i ee : 
the work was published in "1880, and gives a tabular statement 
of the spectra of comets up to 1879. Taking the twelve comets 
There are carbon lines at 559° ae 9 ed 467: 5. 
roa iz. ©. 
Wave le 
Mean of. coabes comets...... 556°4 512°7 470°6 
Recent comet 558'] 513-0 467°3 
Retton tite 558°2 513°9 5 
., Searching for a terrestrial substance that would give a spectrum 
like that of comets, Dr. Huggins found that some of the hydro- 
having 
oi ~ it occurred to to Professor A. W. Wright ae aye 
