GASEOUS SPECTRA UNDER HIGH DISPERSION. 453 



ends; filled the tube with pure Oxygen gas at several atmospheres pressure, 

 looked into it at the near end with a powerful spectroscope, while an incandes- 

 cent lime-light was placed outside the other end ; — and then, pictured on the 

 bright continuous spectrum of that light, — they inform us they saw and 

 measured certain most distinctive bands and groups of dark absorption lines. 

 These were totally different in both arrangement and spectrum place from any 

 of the bright lines of either the high-temperature, or low-temperature, spark- 

 ings already described for Oxygen, — but they were held, nevertheless, to be 

 Oxygen lines, because they were only seen when that one particular gas, in 

 immense excess, was introduced into the tube ; while there was quite lowering- 

 enough of temperature between the simple induction-spark and atmospheric 

 temperatures, to permit of another kind of gaseous vibration being set up, if 

 that was already allowed to be possible, between the simple, and the compound, 

 spark, by reason of the latter's superiority therein. 



The special interest, however, of the St Petersburg experiment, if confirmed, 

 depends still further, and more pointedly, on this other observational fact; viz., 

 that the dark absorption groups which MM. Egoroff and Khamantoff saw 

 in their Oxygen tube they declare to be identical in build, and spectrum place, 

 with the powerful groups of similar dark absorption lines, telluric chiefly, but 

 perhaps partly Solar, or extra-Solar,— seen by all the world constantly in the 

 spectrum of the Sun's light, and so well known there as Fraunhofer's great 

 A and great B. While still more recently M. Cornu in Paris, by an exceedingly 

 elegant method of his own, having lately succeeded in eliminating from the 

 a (Alpha) band of the same Solar spectrum, both the Solar metallic and the 

 terrestrial water-vapour lines, found the residual markings so exactly the 

 counterparts of the now thoroughly understood geometrical construction of 

 the preliminary bands of great A and great B, — that he can pronounce with 

 the utmost certainty for their being all three born of one and the same kind of 

 gas ; though whether, after all, that gas be really Oxygen, the world will be 

 better instructed when other physicists have repeated the bizarre experiments 

 of the Russian capital, and vouched for the purity of the gas introduced there 

 into the long tube. 



Even concerning Oxygen then, our knowledge is but rudimentary, and in 

 fragments; while of Hydrogen, and Nitrogen, how very little have we yet seen 

 of one, possibly two, of the three double phases which the temperature theory 

 indicates must belong to every one of such permanent gases ; and all of whose 

 phases too, our observations in this paper promise will be found replete with 

 the most exact Natural writing, whenever they be efficiently and sufficiently 

 interrogated by man. 



