Since the preceding lines were written, Mr. Huggins and Professor W. A. Miller have continued their researches on the constitution of the celestial bodies by a method of direct simultaneous comparison of the lines in their spectra with the lines in the spectra of many of the terrestrial elements. The spectra for comparison were obtained from the spark of the induction coil taken between points of various metals; and sometimes a platinum wire was used, surrounded with cotton, moistened with a solution of the substance required. The telescope of the instrument was mounted equatorially, and followed the star by clockwork. By this arrangement the spectrum of the star, and the spectrum of the metal compared with it, are seen in juxtaposition; and the coincidence or relative position of a dark line in the stellar spectrum with a bright line in the metallic spectrum can be determined with great precision. It was found that Jupiter’s atmosphere has a much greater absorptive power than the terrestrial atmosphere; that they have some gases or vapours in common, but that they are not identical. Some of the lines seen in the atmosphere of Saturn appear to be identical with those seen in the spectrum of Jupiter. ‘The lines characterizing the atmospheres of Jupiter and Saturn are not present in the spectrum of Mars. Groups of lines appear in the blue portion of the spectrum; and these, by causing the predominance of the red rays, may be the cause of the red colour which distinguishes the light of this planet.’[25] All the stronger lines of the solar spectrum were seen in the brilliant light of Venus; but no additional lines indicating an absorptive action of the planet’s atmosphere. The authors are of the opinion that in most of the planets the light is probably reflected from clouds floating at some distance from the surface, so that it is not subject to the strong absorptive action of the lower and denser strata of the planet’s atmosphere, which, like our own, are most effective in producing atmospheric lines. The results of the observations on the fixed stars are exceedingly interesting, for they show that their elementary constituents are similar, but not identical; and that although they contain many of the sixty-five terrestrial elements, there are probably new unknown substances also.