In a communication[1] to the Paris Academy of Sciences, Deslandres, Bernard, and Bosler epitomised and discussed the various observations of this comet, drawing therefrom some valuable conclusions.
They pointed out that prior to 1907 the only cometary tail spectrum observed was that of the great Comet of 1881, in which the "Swan", or so-called "hydrocarbon" spectrum, was recognised. But in the tails of Daniel's and Morehouse's Comets, new radiations at 456, 426, and 401 were discovered. Also, they disagree with Baume Pluvinel's partition of lines into series.
The presence of a band at 3913⋅2, recognised as belonging to the spectrum of nitrogen at low pressure, and produced by cathode rays, suggests that the cometary matter may be rendered incandescent by the passage of cathode rays emitted by the Sun.
These observers consider that the new spectrum of doublets, and its three principal radiations at 456, 426, and 401, probably constitute the most constant character of cometary spectra, for they appear as intense radiations in the Daniel and Morehouse Comets in which the classical carbon bands showed marked variations.
Thus we see that more recent researches have not tended to simplify the question as to the nature of cometary spectra. Besides the older conception of "hydrocarbons", cyanogen, and reflected sunlight, we have many new lines, probably indicating other substances, to be investigated. But that carbon in one form or another plays an important part in the constitution of comets, is certain; and we now know that in recent comets the cyanogen radiations, especially that at 388, have taken up a large proportion of the comet's light. The ultra-violet character of the light from Morehouse's Comet was a very strong feature which becomes important when we consider the problem of comet photography.
Morehouse, who discovered it by photography, described it as having a conspicuous tail; Borelly, who found it independently, and visually, could see scarcely any tail. An
- ↑ Comptes Rendus, vol. cxlvii, p. 805. March 29, 1909.
