304 On the Temperature and Physical Constitution of the Sun. 



(Tr 



so obtained, ° , would then have to be put equal to m l in 



the above formula — that is, equal to the mass of gas contained 

 in the unit of volume which quantitatively and qualitatively cor- 

 responds with the glowing hydrogen situated in a cylinder of the 

 chromosphere parallel to the visual line and with the unit of sur- 

 face as cross section. 



We then obtain for the density at any place in the chromo- 

 sphere, e. g. at its base, the following expression, 



200000 V 7r' 



or for the pressure, putting for o^ and <x the pressure-values p x 

 and p proportional to them, 



d - p ° a r° • 



Fl ~ 200000 V „' 

 hence, since, according to the preceding, 



__27Sg 

 C -2rat' 



Pi 200000 V wT 



If we take for p the value of the highest pressure employed 

 by Wiillner, aid for t the first of the values found above, we get 



p l = 0-00000000016 millim. mercury. 



Calculated from this for the assumed temperature of incan- 

 descent hydrogen, the density at the base of the chromosphere 

 is found to be about {—) 19 of that of water. A hollow sphere 

 of the size of our earth, filled with gas of this density, would 

 represent a mass of about 84 cubic metres of water. If, then, 

 the chromosphere with an altitude of 10" had everywhere this 

 constant maximum density of its base, its total mass would only 

 amount to (y^) 15 of the mass of the earth. Even with a daily 

 renewal of the entire chromosphere, according to this calculation 

 it would take three million years to consume a mass of hydrogen 

 corresponding to about a millionth part of the mass of the earth, 

 and which may therefore, relatively to the mass of the sun and 

 its atmosphere, be regarded as, to our perceptions, perfectly in- 

 finitesimal. 



[To be continued.] 



