298 



SCIENTIFIC RECORD FOR 1882. 



of September 8, and who obtained the following place for it on the fol- 

 lowing day: 



Cape mean time. 

 September 8, IT*^ 23^ 58* 



R. A. 

 144° 59' 51".4 



Decl. 

 -Oo 45' 30".0 



Mr. Finlay had been more fortunate than the subsequent discoveiers, 

 not only in thus anticipating them by several days, but in being able 

 to retain his hold on the comet right up to its conjunction with the 

 sun; and Mr. Gill was able to inform the Astronomer Eoyal that, "on 

 Sunday, September 17, the comet was followed by two observers with 

 separate instruments, right up to the sun's limb, where it suddenly 

 disappeared at 4^ 50"" 58^ Cape mean time." This observation is wholly 

 unprecedented in the history of astronomy, and proved most valuable as 

 showing how exceedingly unsubstantial the comet was, for the sun's bril- 

 liancy could not, as some have supposed, account for the disappearance. 

 Had it been so bright as to have become invisible, neither bright nor 

 dark, in the center of the sun's disk, it would have appeared as a bright 

 object when seen against the comparatively dull background of the 

 regions near the limb. Had it harmonized with the degree of splendor 

 of the limb, it would have looked dark on the disk. There was not, 

 therefore, enough solid matter, or that matter was not sufficiently aggre- 

 gated, for it to appear as a spot or a cloud, bright or dark, whilst in 

 transit. 



Mr. Hind had meanwhile computed an orbit, which compares as fol- 

 lows with those which Mr. Tebbutt obtained for the 1880 comet, and 

 those of Professor Plantamour for the comet of 1843: 



Comet 1843. 



Comet 1880. 



Comet 1882. 



I'er. pass. 



« 



Q 



Motion 



278° 18' 3".0 



51 4.1 



35 45 39 . 



0. 005807 



Ketrograde. 



277° 22' 53". 4 

 358 22 48 . 6 



36 41 41 .9 

 0. 0067243 



Ketrograde. 



Sept. 17, 2169 

 *270° 14' 36" 

 *346 6 58 

 *37 58 59 

 0. 0080656 

 Retrograde. 



*App. eq., Sept. 25. 

 Sun's radius 0.004664 (sun's mean distance = 1). 



But this orbit would give the comet's distance from the center of the 

 sun at the time of Dr. Gill's remarkable observation, on September 17, as 

 only 10'.9; that is to say, it should have been far on the disk, and fully 

 5' from the limb at the time when it was actually seen to be only just 

 entering the limb. Mr. Hind cannot think this discrepancy due to 

 faults in the elements, for they represent the middle position within 1', 

 and the first observation was taken only twenty hours after the one at 

 the Cape with which the elemeuts are in so little accord. There is, 

 therefore, strong reason to believe that the comet's sj)eed received con- 

 siderable alteration whilst in the immediate neighborhood of the sun, 

 and Mr. Hind suggests the probability of its return in October, 1883. 



