XIV NOTES BY THE EDITOR. 



However small these caverns may be in special cases, the spe- 

 cific gravity of the enclosed gases cannot be greater than that of 

 the surrounding liquid, because, otherwise, the compressed gases 

 would sink towards the sun. 



Professor Zollner finds that, calling the pressure at a certain 

 height above the base of the solar atmosphere, between 0.500 m. 

 and 0.050 m., there results a mean temperature of 27,700. 



Iron must accordingly exist as a permanent gas in the solar 

 atmosphere ; from the value of t = 27,700 the inner temperature is 

 found to be 68,400, and the pressure in the interior of the space 

 from which the protuberances emanate is 22.1 times greater than 

 the pressure at the surface of the liquid separating layer ; the pres- 

 sure at the base of solar atmospheres being 184,000 atmospheres, 

 that at the interior would be 4,070,000 atmospheres, this latter 

 maximum pressure being reached at a depth of 139 geographical 

 miles below the sun's surface. 



The pressure increasing rapidly towards the interior of the sun, 

 permanent gases, such as hydrogen, can exist only in a glowing 

 state in the interior of the sun. 



Professor Zollner shows that the quantity of oxygen and nitro- 

 gen, if these gases exist in the sun's atmosphere, must be ex- 

 tremely small compared with that of hydrogen in that stratum 

 where the spectrum of hydrogen becomes continuous, and their 

 pressure consequently would not be indicated by absorption. 



The absence of oxygen and nitrogen lines in the solar spec- 

 trum may also be accounted for by the slight emissive power of 

 permanent gases as compared with that of vaporized solids. 



Professor Zollner concludes : 



1. The absence of lines in the spectrum of a self-luminous 

 star does not prove the absence of the corresponding bodies. 



2. The stratum, in which the reversion of the spectrum takes 

 place, is different for every body, and lies nearer to the centre 

 of a star the greater the density of the vapor and the less the 

 emissive power of the body is. 



3. In different stars this stratum, other things being equal, 

 lies the nearer the centre the greater the intensity of gravi- 

 tation. 



4. The distances of the strata of reversion for different bodies 

 from the centre of the star, and from each other, increase with 

 the temperature. 



5. The spectra of different stars contain the more lines under 



