82 SPECTRUM AND APPEARANCE OF THE RECENT COMET. 
The spectroscope I used was by Browning, and capable of clearly 
dividing the D lines, and the measures were made by means ofa 
micrometer. While working at the comet I was unable to use 
artificial light, and therefore adopted the method of making the 
lines disappear behind a bar in the field of view, with very sau | 
factory results. For the purpose of securing the exact positions 
of the bright lines, I turned the telescope to the moon then shining 
and measured the nearest Fraunhafer lines while the micrometét 
was in the same position as it was when used for the comet. 
Turning the telescope so that the slit of the spectroscope T 
ceived light from the tail of the comet, I found it was too aint to 
admit of good measures to the centre of each. The middle line was 
by far the brightest; the next in brilliance was in the yellows 
and the third and faintest was in the violet. ‘The whole Mam 
spectrum increased in brightness as the slit approached t 
but when the nucleus itself was on the slit all the additional : 
seemed concentrated in the middle of the B line until it shone 
almost like a star, and quite as bright as the nucleus — at 
ing that its light is monochromatic. Even in the brig est part” 
the comet I was unable to see any dark lines in the contmue™ 
spectrum. I think the reason was its faintness, 
reason to doubt that at least part of it 18 caused my 
sunlight ; but our atmosphere or gases in the § int it 
us would not reflect so much light as the comet does; 
‘seems probable that highly heated solid matter 
of it. The solar heat at that distance from t 
no m 7 : ; 7 
cence such as the bright lines prove the gas to be in- °. ward 
for the observed facts se eicl theories have been put frictio® 
agitation as it approaches the sun, and that this shines fn set 
discharge. Another is that it is due to chemical of aS 
up as the comet approaches the sun. In su roach oUF © 
may be said that meteors burning as they ap ‘5 indicate 
give spectra with bright metallic lines which see! ae 
must give me 
he comet ka 
‘y 
