Page:Popular Science Monthly Volume 22.djvu/310

296 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, traversed 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 spectroscope 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 conspicuous. 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 proportion 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 collected and published, something will be found to supply what is so unfortunately wanting in Ricco's most interesting but incomplete observation—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 country 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.