264 The Great Comet of 1861. 
by the earth at a distance of 0:031. This result however rests 
upon the supposition that the tail lay in the prolongation of the 
radius vector. In fact, it appears to have been curved in the 
plane of the orbit, so that the remotest particles of the tail passed 
through the plane of the ecliptic earlier than the nucleus. But 
in no case, did any collision take place. According to the above 
hypothesis, the least distance of the earth from the nearest of the 
tds particles was 0-025 at about 12 hours after the passage of the 
comet through the node.” 
Altona, July 9th, 1861. 
The above calculations of Pape relate to the straight bright 
‘ray. There was, however, as will be seen by reference to the 
preceding part of this notice, a great mass of diffuse light which 
separated from the ray, and swept off towards Corona Borealis 
in the early part of July, reaching on the 4th to a distance 
of 40° from the nucleus, and having a breadth of 12° or 15°. 
This would have barely grazed the earth on the 30th of June. 
In a late number of the Bulletin of the Imperial Observatory at 
Paris, Mr. Hind suggests that a peculiar illumination of the 
sky noticed in England on that date was possibly “attributable 
tu the commingling of the matter forming the tail of the comet 
with the earth’s atmosphere.” The observations on this day have 
a peculiar interest, from the fact that, at about 10" mean time 
Greenwich, the earth passed the plane of the comet’s orbit, and 
the outline of the tail presented to us was that of the section 
formed by a plane perpendicular to its orbit. : 
From its brilliancy and nearness to the earth, the opportunity 
of defining this section was perhaps the best which the history 
of astronomy has afforded. It is to be hoped that European 
' astronomers, who it seems had the advantage of clear skies 4 
a favorable position of the comet at the very hour of our crossing 
the orbit, have made good use of the occasion by recording care- 
fully all peculiarities of the physical aspect. 
ecchi has defined the position of the tail at 11 30™ m.t. fia 
at Rome, June 30, about 55™ after the earth’s passage throug 
the orbit plane. Comparing the position of an are of a 
circle drawn from the sun through the nucleus, which must have 
corresponded almost precisely with the projection of the plane 
of the orbit, we find that at the pole star the centre of the ray 
was about 14° to the east of the circle. 
At aLyre the eastern edge was at the same distance to the 
west of the circle, so that the entire breadth was on that side; 
the ceatre being distant 
14° +4 (breadth of tail). 
Again at ¢ and e Aquile the tail was about 4° to the east of 
the circle. There was therefore a decided bend in the 
