158 Liming and Dewar — Spectrum of the more 



exception that in passing from the vessel into which the first 

 fraction of liquid air was distilled it was not passed through a 

 U-tube immersed in liquid hydrogen on its way to the 

 exhausted tube. In consequence it contained traces of nitro- 

 gen and argon, and when sparked showed the spectra of these 

 elements as well as those of hydrogen, helium, etc. The 

 nitrogen spectrum disappeared after some sparking, but the 

 tube still shows rays of argon as well as those of the gases in 

 the other tubes. On examining the spectrum of the negative 

 pole in the neighborhood of the principal green ray, a weak 

 ray was seen in addition to those given by the other tubes. It 

 was found by comparison with the nitrogen rays X 5002*7 and 

 X 5005*7 to be a little less refrangible than the latter of these 

 rays, and by measuring its distance from the nitrogen rays and 

 from the two helium rays 4932*1 and 5015*7. 



With a micrometer eye-piece, the wave-length X 5007*7 for 

 the new ray was deduced. This looks as if we might find the 

 substance which is luminous in nebulse to be really present in 

 the earth's atmosphere, and we hope shortly to be able to 

 verify the observation of it. 



Turning to the coronal rays, our tubes emit a weak ray at 

 about X 5304. This is not far from the wave-length X 5303*7 

 assigned by Sir JST. Lockyer to the green coronal ray. It is, 

 however, greater than that assigned by Campbell, namely, 

 5303*26.* Other lines observed by us near the places of coro- 

 nal lines are at wave-lengths about 4687, 4358, 4570, 4323, 

 4232, 4220, 3985, 3800. ^These are all weak lines except that 

 at X 4232, which is of tolerable strength, and that at X 4220 

 which is rather a strong line. The wave-lengths 4323, 4232, 

 4220, and 3800 come very close to those assigned to coronal 

 rays, but the others hardly come within the limits of probable 

 error. The ray 4220 seems too strong in proportion to the 

 others, but the strength of that at 4232 seems to accord with 

 the strength of the corresponding ray in the corona. It will 

 be seen that the rays we enumerate above correspond approxi- 

 mately to the stronger rays in Sir N. Lockyer's list.f Further 

 measures of the wave-lengths of the faint lines are needed 

 before we can say definitely whether or no we have in our 

 tubes a substance producing the coronal rays, or some of them. 



As to the auroral rays, we have not seen any ray in the 

 spectrum of our tubes near X 5571*5, the green auroral ray. 

 We have observed two weak rays at X4206 and X 4198 which 

 may possibly, one or both represent the auroral ray X 420. 

 The very strong ray of argon, X 4200*8, would make it prob- 

 able that argon was the origin of this auroral ray, if the other, 



* Astroph. J., vol. x, p. 190. 



f Roy. Soc. Proa, vol. lxvi, p. 191. 



