64 REVIEWS—-DONATI'S COMET. 
attrazione della cometa e perduta. Questa materia era sempre visibile 
dalla parte della curvatura interiore della coda la quale riusciva percié 
mal terminata, mentre la esteriore era benissimo decisa.’’ 
The two secondary tails or streamers in this comet have been already 
noticed ; they were much fainter than the real tail, whereas in that of 
1861 (1), the streamer was decidedly brightest. A curious bulging 
out of the head into a sort of large horn, was observed in the early 
stage of the comet on the side towards the sun, at an angle of some 
forty degrees or so; an appearance so singular that its reality might 
have been doubted had it not been confirmed by its recurrence towards 
the end of the comet’s course, testified from an opposite part of the 
world. . 
Another peculiarity seen for the first time, we believe, in this comet 
was the so-called ‘‘ columnar structure’’ of the tail, the broad end of 
it being cut up by parallel dark bands, the direction of which did not 
appear to be referrible to either the axis of the tail or the sun. The 
two branches of the tail, coalescing after running some length, left 
between them a less illuminated space, to which the name of the “ dark 
zone’’ has been given, varying much at intervals in extent and never 
sharply outlined ; but within this was noted a “ dark canal,” proceed- 
ing direct from the nucleus with its breadth continued uniform, and 
traceable for a good way even into the brighter part of the dark zone. 
It is described as being at its origin “almost black,” and might tempt 
us to fancy it an actual shadow of the nucleus, if it were not that its 
position, deviating some degrees from the sun, forbad the supposition. 
Of the outer faint “veil,” or nebulous envelope dimly surrounding 
the head and tail, and sharp in its outer edge, little is to be said ex- 
cept that it was not symmetrically placed with regard to the nucleus, 
and was so delicate an object that it escaped the attention of nearly all 
the observers.* But the most important result of all, and one for 
* There do not appear to have been observed any of those pulsations or coruscations of an 
auroral character, which are recorded in other cases,—as for instance when Kepler tells us 
that the tail of the comet of 1607 would in the twinkling of an eye become very large, and in 
several other cases where the tail exhibited undulations as if it had been blown by the wind» 
and in more recent times, the great one of 1843 shot out in One evening a new tail inclined 
at 18° to the other and twice as long, never seen again. The only notice we remark is by 
Mr. Spalding at Selby, Hng., who says :— 
* A sudden and momentary emanation from the nucleus was remarked. At first it was 
supposed to be due to atmospheric causes; but from its recurring in precisely the same form, 
the author felt convinced that it was really attributable to a change in the nucleus.” 
“ Appearances of a similar nature continued to be observed during the visibility of the 
comet.” 
It is odd that no other observer saw them in this instance, but we think there can be no 
doubt of the reality of such momentary pulsations existing, aud that Olbers is entirely 
astray when he assigns their origin to atmospheric causes. 
