314 Prof. F. Zollner on the Temperature and 



the interior and those on the surface of the sun. The possibility 

 of such a difference of pressure, however, necessitates the exist- 

 ence of a zone of separation between the interior and exterior 

 masses of hydrogen, the latter of which has been shown to form 

 an essential portion of the solar atmosphere. 



The supposition of such a layer of separation is so forcibly im- 

 pressed on the mind on the first sight of such an eruptive pro- 

 tuberance, that it even suggests itself to observers who, like 

 Respighi, suppose that electricity may be the cause of these solar 

 volcanic phenomena. 



If, however, we admit only the simpler and therefore more 

 probable hypothesis of the difference of pressure, we have before 

 us a phenomenon which, by the application of the mechanical 

 theories of heat and of gases, may be made to yield us most im- 

 portant conclusions concerning the temperature and physical 

 constitution of the sun. The object of the present communica- 

 tion is to exhibit the fertility of this mode of attacking the 

 question. 



The mechanical theory proves for perfect gases : — 



(1) The law of Mariotte and Gay-Lussac. 



(2) The constant relation of specific heat with constant volume 

 and with constant pressure. 



These constants, determined by means of well-known methods 

 for a given gas, must therefore, from the point of view of the 

 mechanical theory of gases, be considered unalterable, in the 

 same way as the atomic weight of the elements ; and they cer- 

 tainly must not be placed in the category of other empirical con- 

 stants, such as the conductive power of bodies for heat, or the 

 coefficients of expansion of solid or liquid bodies. These con- 

 stants only apply within the limits for which they have been 

 ascertained by experiment, and altogether lose their significance 

 when applied far beyond these limits. 



Upon this assumption I consider the eruptive protuberances 

 as a phenomenon of the issue of a gas from one space to another, 

 in such a way that the pressure during the issue in both spaces 

 is supposed to be constant, and so that no absorption or evolu- 

 tion of heat occurs. 



Let A signify the heat- equivalent of the unit of work ; 



v the initial velocity of the gas in the plane of the outlet ; 



g the intensity of gravity on the sun ; 



k the relation of the specific heat of the gas with constant 



pressure and constant volume ; 

 c the specific heat of the gas with constant volume reduced 



to an equal weight of water ; 

 U the absolute temperature of the gas in the interior space 

 whence the gas issues ; 



