H. and K. lines of the Solar Spectrum . 2t£7 



of the discharge just as the metallic vapor does in dry air. The 

 edges of this spark show a strong red tint and give the line spec- 

 tram of hydrogen. The center of the spark is of a brilliant 

 whiteness. Strong bands appear in the position of the reversed 

 lines which I have obtained with rarified hydrogen, in the quartz 

 tubes.* There is evidently a chemistry of the electric spark in 

 relation to the appearance of certain lines of the constituents of 

 atmospheric air. The discovery of argon shows this. I am at 

 present working upon this question with still more powerful 

 sparks. The commercial employment of high voltages and 

 great current strength should permit more powerful means in 

 spectrum analysis than have hitherto been employed. 



The continuous spectrum observed with disruptive discharges 

 in gases occurs also when electrical discharges are obtained in 

 distilled water and in certain other liquids. Prof. Wilsing,f 

 G. E. Hale,;}: and Lockyer,§ have discussed the reversed lines 

 observed under this condition. The phenomenon of continous 

 spectrum and of reversals obtained by the investigation is, I 

 believe, of the same nature as that observed by me in gases. The 

 continuous spectrum is due to a sudden compression of the 

 medium under the powerful disruptive electrical explosion, and 

 the reversals are due to a solarization and not to a reversing 

 layer. The reversed lines observed by me increase in 

 intensity with repeated discharges. The action appears to be 

 most pronounced toward the ultra-violet. This is the case also 

 with the reversed lines observed under water. 



The conclusions, therefore, of my first paper on reversed lines 

 in this Journal for July, 1902, are confirmed by further inves- 

 tigation. At the basis of the great H.H. lines of the solar 

 spectrum there are strong gaseous lines, which I believe are 

 oxygen lines. The reversed lines which apparently coincide 

 with certain calcium lines are not due to calcium but are gaseous. 



The phenomena of photographic reversals is of great 

 importance in the study of changes going on in the sun. The 

 accompanying plate show the normal spectra which illustrate 

 this article. Fig. 1 represents the gaseous lines which closely 

 correspond with the great H.H. lines of the solar spectrum. 

 See also fig. 3, in my article in this Journal, July, 1902. 



Fig. 2 represents the spectrum of calcium in the neighbor- 



* It seems probable that these lines, and also the great H.H. lines of the 

 solar spectrum, are due to oxygen. At very high temperatures the disso- 

 ciated oxygen may be free to vibrate in its own periods. It does not seem 

 inconceivable, therefore, that many spectral lines attributed to metals may 

 be oxygen lines. 



|H. Kavser, 1. c, i, p. 228. 



XG. E. Hale, Astrophys. Jour., xv, 1902. 



§N. Lockyer, Proc. Roy. Soc, lxx, 1902. 



