262 
CAPTAIN W. DE W. ABNEY AND DR. A. SCHUSTER 
to be the case. The nucleus is exceedingly well and sharply defined, the tail is 
somewhat curved ; it did not point towards the sun’s centre, but in a direction 
nearly tangential to the limb. The extent of the tail was roughly two-thirds of 
a solar diameter. 
Our photographs allow us to fix the position of the comet. It appears that the 
nucleus was at a distance of 45' 50" from the sun’s centre during the middle of the 
eclipse, and that the line joining the comet to the sun’s centre made an angle of 
16' 27" with the circle of declination towards the west. Professor Tacchini (C.R, xcv., 
p. 896, 1882 ; Memorie della Societa degli Spettroscopisti Italiani, vol. xi., 1882) 
gives slightly different values. According to him the' comet’s position was : Dec. 
18° 30' 17" N., RA. 3 h 35 m 16 s . This would give a distance of 52' 26" from the 
sun’s centre, and a position angle of 68' 09", 21' 51". According to our measurements 
the position of the comet at 18 h 24 m 36 s G.M.T. was— 
Dec. 18° 34' 59" N. 
RA. 3 h 34 m 43 s . 
An examination of our different photographs shows a slight but progressive change 
in the comet’s position. This is in part accounted for by the moon’s motion over the 
solar disc during the eclipse, for the position of the comet had of course to be referred 
to the dark lunar disc. The change in the distance of the comet from the moon’s 
centre is however slightly larger than can be accounted for by the motion of the 
moon, and is probably in part due to the proper motion of the comet, which in that 
case must have moved away from the sun during the eclipse. The motion, if it 
exists, must however have been very small, and as the matter presents very little 
importance we have not investigated it further, especially as the comet in all 
probability will not be heard of any more. The different eclipse parties present at 
Sohag decided at a joint meeting after the eclipse to give the name of Tewfik 
to the comet, in recognition of the Khedive’s generous hospitality. 
Results of the prismatic camera. 
This instrument consisted, as has already been explained, of a camera the 
lens of which had an aperture of 3 inches, and a focal length of 20 inches in 
the yellow. The prism, which was placed directly in front of the lens, had a 
refracting angle of 60°. The line of dispersion projected on the celestial sphere ran 
nearly north and south, the less refrangible side being towards the south. Only one 
plate was exposed, and that for 65 seconds. The first impression gained by an inspec¬ 
tion of the photograph thus obtained would lead one to believe that sufficient care 
was not taken in focussing the camera. As before stated, however, it was quite impos¬ 
sible to have the whole of the spectrum in focus at the same time, and as special atten¬ 
tion was directed to the less refrangible part in this instrument, it is obvious that 
