Page:The story of the comets.djvu/242

188 of band at 388 to be the only representatives of the cyanogen spectrum, and recorded a very persistent continuous spectrum. The three strongest bands of unknown origin were those at 456⋅1, 426⋅7, and 401⋅3 previously recorded by Evershed in the spectrum of Daniel's Comet.

Another similarity of these two comets was found in the fact that some of the bands were double.

The results obtained by Frost and Parkhurst, at the Yerkes Observatory, exhibited points of variance with both sets of the French observations. Twenty-one spectrograms were obtained between October 28 and December 2, 1908, and on none was there a trace of continuous spectrum, thus showing that at that epoch the amount of reflected sunlight was very small as compared with the amount of intrinsic light emitted by the incandescent carbon and other matter. [See Fig. 101, Plate XXVI.]

Allowing for the uncertainty of wave-length measures made on photographs of small dispersion, it appears that both the hydrocarbon and cyanogen spectra are probably represented. Relative variations in the intensity of the tail images indicate some difference between nuclear and tail matter which is not explained by the behaviour of the matter concerned when experimented upon in the laboratory.

An important feature of these spectra is that the separate monochromatic images of the tail follow the bends seen on the direct photograph, thus showing that particles having the same chemical constitution were ejected at angles differing by as much as 40°. Apparently we have, in this, a contradiction of Bredichin's theory, according to which the comparatively straight tails shown on these photographs should have been seen only in hydrogen radiations and not in those of the hydrocarbons and cyanogen.

Campbell and Albrecht made visual and photographic observations, using, for the latter, a specially designed spectrograph in conjunction with the 36-inch Lick refractor. Their results showed the presence of carbon and cyanogen, although the second cyanogen band was, apparently, entirely absent.