Pressure at the Surface of the Sun and Stars. 125 



(1) Very often, if a spark traverses a mixture of gases, one 

 gas only becomes luminous. This result has recently been 

 confirmed by the photographs of H. W. Vogel. 



(2) A gas may, by means of an electric discharge, be made 

 luminous below 100° C. 



I have concluded from my investigations that the electric 

 discharge increases the oscillatory energy of a gas indepen- 

 dently of its translatory motion; and I compared these pheno- 

 mena to fluorescence. 



Hasselberg has confirmed my results, and has drawn some 

 conclusions from them concerning the aurora borealis, comets, 

 &c. I did not in my first communication refer to these mat- 

 ters, as I hoped first to be able to make some experimental 

 investigations in order to fix the relations existing between 

 pressure, luminosity, and quantity of electricity ; but I had 

 thought of these evident applications. 



The curious forms of prominences which rise and float freely 

 over the solar surface, and which Lohse has tried to refer to 

 chemical processes, may also be explained by electrical causes. 



The two results which I have mentioned must render us 

 very cautious before we apply results arrived at by means of 

 the electric arc or vacuum-tubes to solar phenomena. I 

 believe that we cannot at all employ them for the determina- 

 tion of temperature and pressure. 



It is by no means necessary that we should have the same 

 relative intensity of the lines in the spectra produced by the 

 two different causes. The effect of the electric discharge is 

 first of all to displace the aether spheres surrounding the mo- 

 lecules ; and the vibrations which are caused are in the begin- 

 ning independent of the translatory motion, which latter 

 chiefly determines the temperature. By means of the encoun- 

 ters of the vibrating molecules the rotatory motion is changed 

 into translatory motion ; and then only is the temperature 

 raised so high that the gas may become luminous owing to 

 its heat. This may take place in the narrow parts of a 

 Geissler tube. 



If, on the other hand, we produce spectra by means of heat- 

 ing only without calling electricity to help, we first of all in- 

 crease the translatory motion, which must be increased consi- 

 derably; for the gas becomes luminous, and then the changes 

 in the forces binding the atoms together to a molecule must 

 affect the spectrum. 



At any rate we must carefully investigate the effects of the 

 electric discharge on the nature of spectra before we can draw 

 any conclusions from spectra produced by electricity on ques- 

 tions relating to temperature and pressure. I intend to dis- 

 cuss this point in another paper. 



