Page:The story of the comets.djvu/234

180 spectrum on June 29 showed the Fraunhofer lines, F being unmistakeably present. But the photographic plate had anticipated the eye of the observer, Huggins's negative taken on June 24 showing in the ultra-violet region both the hydro-carbon bands and the solar absorption lines, and proving that the spectrum in the visible portion and in that beyond the grasp of the eye were essentially the same.

The spectrum of the tail of this comet was also examined, and both Vogel and Young traced the carbon bands far down its length, the former indeed to its very end. Probably the spectrum of reflected sunlight was also present, though Young could not trace it so far as he could the gaseous flutings.

Comet iv. of 1881 (Schäberle's) formed a striking contrast to Tebbutt's, in that it gave almost a pure spectrum of bands. The hydro-carbons were strongly in evidence; of reflected sunlight there was scarcely a trace.

Both these comets afforded to Copeland and Lohse a further proof of the origin of their banded spectra, for these observers were able not merely to see simple shaded bands, but to break them up into true flutings precisely as the hydro-carbon spectrum can be resolved.

The Comets of 1882 were yet more important. All the comets which had been previously examined had considerable perihelion distances; Comets i. and ii. of 1882 both approached very near the Sun, the latter all but grazing its surface. The former, known from its discoverer as Wells's Comet, at first showed an almost purely continuous spectrum. The nucleus was greatly condensed, and to direct eye observation and as seen through the prism, it presented a very stellar appearance. On May 27 Copeland suspected the presence of a bright line; the next night the line was seen to be coincident with the D line, and as the result of what he saw on May 29 Copeland wrote :—

"The spectrum of the nucleus of Wells's Comet deserves the closest attention, as it shows a sharp bright line coincident with D, as well as strong traces of other bright lines, resembling in appearance those seen in the spectra of γ Cassiopeiae and allied stars."