296 THE POPULAR SCIENCE MONTHLY. 



showing that the principal brilliancy of the comet was not reflected 

 sunlight. The usual carbon bands of the cometary spectrum were 

 not visible through the sky illumination, and no other bright lines 

 except those of sodium were seen by Thollon. On the 22d the comet's 

 spectrum was observed in the early morning just before sunrise by 

 Ricco, of Palermo. He reports his observation thus : " The spectrum 

 was formed of the narrow continuous spectrum of the nucleus, trav- 

 ersed by a large and strong line of sodium (D) ; by enlarging the slit 

 I saw a globular, monochromatic image of the nucleus and coma. 

 Besides the line of sodium many others were present, but, my spectro- 

 scope not having a micrometer, I did not determine them. I observed 

 a band in the red, a line in the yellow near and after D, two others in 

 the green, and an enlargement of the continuous spectrum in the 

 green and blue." It is exceedingly unfortunate that the position of 

 these lines could not have been determined, at least approximately. 

 No one can predict when such an opportunity will occur again. 



The weather in this part of the country was abominable up to 

 November. The writer attempted to get spectroscopic observations 

 on September 20th, but was foiled by clouds, and has since succeeded 

 only on October 2d, 4th, 10th, 15th, and 24th. On the first of these 

 dates the sodium-lines were still easily visible, though not conspicu- 

 ous. The carbon bands were magnificent, especially the brightest 

 one (in the green), in which could be clearly seen the three fine lines 

 observed in the spectrum of Coggia's comet. The band in the violet 

 was very faint. The nucleus gave a strong continuous spectrum, on 

 which the carbon bands were superposed ; and in the tail the pro- 

 portion of white light (continuous spectrum) to carbon light appeared 

 to be about the same as in the nucleus. The bands could be followed 

 far out into the tail by widening the slit, but were lost before the 

 continuous spectrum quite vanished. No dark lines were made out. 

 On the 4th the results were the same, except that the sodium-lines 

 were very hard to see, and they disappeared entirely before the next 

 date. The later observations added nothing more. It is much to be 

 hoped that, when the different results of all observers come to be col- 

 lected and published, something will be found to supply what is so 

 unfortunately wanting in Ricco's most interesting but incomplete ob- 

 servation hiatus valde deflendus. 



The highest interest of the present comet lies in its orbit, however, 

 its relation to preceding comets, and its possible speedy destruction by 

 the sun. Almost as soon as it appeared, Professor Boss in this coun- 

 try and Hind in England proposed the hypothesis that it is identical 

 with the great comet of 1880, the period of the latter comet having 

 been shortened by some resistance. If so, this comet will be back 

 again in a few months, and before long must fall upon the sun. They 

 have weighty arguments on their side, but on the whole a different 

 conclusion is more probable. 



