Nov. 30, 1882] 
NATURE 
109 
It will be remembered that the first spectroscopic ob- 
servations, by M. Thollon, at Nice, reported the spectrum 
of the nucleus as continuous, very brilliant, and much 
extended toward the violet. The head gave the sodium 
lines very brilliant, clearly double, and appearing dis- 
placed toward the red. This report was confirmed on the 
same day by a similar one from Mr. Lohse, with the 
additional remark, that he saw many bright lines, the 
sodium being the brightest, and all apparently displaced 
toward the red. 
October 15. This state of things had entirely changed. 
The change had probably been gradual, and was de- 
pendent upon the distance of the comet from the sun. 
G 
| 
No. 1.—Spectrum of Crul’s Comet, October 15 and 16. 
The first observation made on September 18, when the 
comet was near the sun, gave a continuous spectrum, 
hich was due to the strong reflected light, while the 
bright lines were due to the vapours developed by the 
intense heat of the sun. 
On October 15 the spectrum resembled the spectra of 
the comets of 1868; of the sodium line there was no 
trace, although the spectrum contained light of about the 
same refrangibility. The tail of the comet gave a faint 
but apparently continuous spectrum brightest in the 
green. 
A somewhat similar change was observed, I believe, in 
the spectrum of the Comet Wells as it approached the 
sun, except that its nucleus gave always a continuous 
spectrum, to which was added the sodium line as the 
comet neared the sun. If we are soon to witness a 
return of the September comet, it is desirable that many 
observers should be prepared to watch the changes as 
the comet approaches the sun. 
Sketch No. 2 represents the comet as it appeared in 
the comet-seeker on the morning of October 10, which 
No. 2.—October ro, 1882, 
was particularly clear. This outer envelope I first 
noticed on the morning of the 8th, when I traced it far 
beyond the head of the comet in the direction of the sun, 
but only on the east side. On the 1oth it appeared as 
represented in the sketch. The outer edges were per- 
fectly sharp and parallel to the axis of the comet, thus 
forming a cylinder whose diameter was about four times 
the diameter the tail measured several degrees from the 
head. 
When I again looked for this envelope on the | 
25th, it could be traced only on the east side, but retained 
the same relation to the tail. The greatest length to 
ee this attained was about four degrees beyond the 
head. 
Sketch No. 3 represents the head of the comet as it 
appeared on October 25 in the 26-inch equatorial. Owing 
to the low altitude of the comet, this instrument had not 
been used before. The head appeared more elongated 
than at any time before but instead of the uncertain, 
delusive appearance which it presented in the ro-inch 
equatorial, the image brought out the peculiarities of each 
portion of the head, and left little doubt that there was, 
at that time, an essential difference between the central 
portion or nucleus proper, and the other two portions. 
The central part was circular, of considerable apparent 
No. 3.—Nucleus of Comet, October 25, as seen in 26-inch Equatorial. 
diameter, and of quite uniform brightness throughout. 
The other two portions were irregular in shape, much less 
bright than the nucleus, and their brightest parts were 
also irregular in shape. Both were apparently separated 
from the nucleus, though on its side they were joined to 
each other. The portion extending in the direction of 
the tai] was the longest and brightest. 
The next opportunity to examine the comet was op 
November 3, when it had decidedly changed in appear- 
ance, as represented in No. 4. The nucleus remained as 
when last seen, as did also the portion of the coma 
nearest the sun. The other portion showed a circular 
No. 4.—Nucleus of Comet, Nov. 5, 1882, as seen in 26-inch Equatorial. 
condensation almost as distinct as the original nucleus, 
and about two-thirds its size ; still further in the direction 
of the tail was another condensation, smaller and less 
distinct than the second. On November 6 these con- 
densations were still more pronounced, and shone with a 
much stronger light than the coma in which they were 
enveloped. 
The following micrometric measurements were made 
on the 3rd and 6th, using the 26 in, equatorial :— 
