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242 On the Physical Appearance of the Comets b and c, 1881. 
perhaps equivalent to the “dark segment” mentioned in the remarks belonging to 
Fig. 3. Finally it may be mentioned that there were certainly not even traces of 
concentric rings visible in the coma, as have been frequently observed in other 
comets. 
On searching for drawings of other comets, which might be compared with mine, 
I did not find any which bear a greater resemblance to them than Bessel’s draw- 
ings of Halley’s comet, in the ‘‘ Astronomische Nachrichten,” of February, 1836, 
(Vol. XIII.).* The similarity between the two comets, as represented by the 
drawings is so great, that Bessel’s description is of good service in explaining the 
different features of Comet b, 1881. The only difference between the two series of 
drawings is, that Bessel observed throughout the dark segment cut out of the 
coma, whilst he does not record any instance of the lght-fan (“ Ausstrémung ”) 
consisting of different rays, as in my drawing Fig. 5. The different situations of 
the light-fan in my drawings mentioned above prove, when compared with Bessel’s 
description, that Comet b showed the oscillating motion of the lhght-conoid pro- 
ceding from the nucleus (“die drehende oder schwingende Bewegung des aus- 
strémenden Lichtkegels”) rather strongly developed. and it is to be hoped, that 
this point in particular may be more thoroughly investigated by means of draw- 
ings of other observers. 
Not much is to be derived from the two drawings of Comet ¢ (Pl. XIX., Figs. 7 & 8), 
some striking differences from the preceding comet are, however, set forth by them, 
which deserve mention. The radius of the coma was smaller, the nucleus was not 
quite so well and sharply defined (this is not sufficiently shown in the plate), and 
the light, proceeding from it, more gradually decreasing. The coma, equally 
without concentric rings, was interrupted by a darker segment in the apex, sug- 
gesting nebulous matter flowing fountain-like from the nucleus towards the tail. 
The part behind the nucleus—the ‘“ shadow’—was shaded off to a sharp dark 
line, which, however, became invisible, or disappeared, during the observation. On 
the whole, the description proves that the comet was subject to rapid changes 
on the night of the 19th August, since the different statements can hardly be 
attributed to atmospheric influences only. The most interesting and remarkable 
feature is the “inverted fan” in drawing Fig. 8, representing a direct emanation 
of nebulous matter from the nucleus towards the tail—another point, where 
more light is to be expected from a comparison with other observations. 
* Reprinted in Johann Carl Friedrich Zotlner, Ueber die Natur der Cometen. 
