The first successful application of the spectroscope to comets was made by Donati in 1864—the light of the comet being then divided into three bright bands, whose position, however, was not exactly determined. In 1866 Dr. Huggins obtained two kinds of light from a telescopic comet, part of the comet’s light giving a continuous spectrum, probably reflected sunlight, the other a spectrum of three bands. In 1868 a comet was observed (Brorsen’s) with more success. Three bands were seen in the spectrum of the light from the comet’s head, and a comparison of these with measures of similar bright bands belonging to the spectra of various combinations of carbon, showed, or rather seemed to suggest, that “combinations of carbon might be present in the comet.” “In conjunction with my friend, the late Dr. W. Allen Miller,” says Dr. Huggins, “I confronted directly with the spectroscope attached to the telescope, the comet’s light with that from inductive sparks passing in olefiant gas. The sensible identity of the two spectra left no doubt of the essential oneness of the cometary stuff with the gas composed of carbon and hydrogen that was employed for comparison.” “Since that time,” proceeds Dr. Huggins, “the light from some twenty comets has been examined by different observers. The general close agreement in all cases, notwithstanding some small divergences, of the bright bands in the cometary light with those seen in the spectra of hydrocarbons, justifies us fully in ascribing the original light of these comets to matter which contains carbon in combination with hydrogen.” Last year photography was applied to this spectroscopic work. The spectrum of the brightest comet of that year was partly continuous, and on this continuous spectrum many of the well known Fraunhofer lines could be traced. This made it certain that part of the comet’s light was reflected sunlight; though Dr. Huggins considers also that a part of the continuous spectrum of every comet is due to inherent light. On this point some doubts may be permitted. It is one thing for special bands to show themselves, for some substances may become self-luminous under special conditions at very moderate temperatures; it is quite another thing that the solid parts of a comet’s substance should become incandescent. I venture to express my own belief that this can scarcely happen except in the case of comets which approach very near to the sun. Besides the continuous spectrum with dark lines, the photograph showed also a spectrum of bright lines.