44 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



the number of assumptions are fewer and simpler. Zollner's 

 new method for the determination of the solar temperature 

 requires only one single theoretical assumption, viz., the law 

 of Mariotte and Gay-Lussac; and but one empirical assump- 

 tion, viz., the knowledge of the ratio of the densities of the 

 aqueous portion of the atmosphere at two different distances 

 from the solar surface. The spectroscopic study of the solar 

 limb allows us to investigate the so-called chromosj^here, 

 which is an important portion of the atmosphere, and to de- 

 termine the mean altitude of this layer, wherever there are 

 protuberances to disturb the equilibrium. If, then, we were 

 able to determine, even roughly, the ratio of the pressures or 

 of the densities on the upper and lower limits of the chro- 

 mosphere, we should be in possession of the above-mentioned 

 desired data, by the use of Avhich we should be able to ascer- 

 tain the mean value of the temperature of the chromosphere. 

 Zollner, in accordance with these views, shows that it is, in 

 fact, possible to determine approximately the ratio of the 

 pressures at the base and at the upper limit of the chromo- 

 sphere. According to the observations made by WtiUner, 

 he shows that the change of pressure from 2000 millimeters to 

 one millimeter produces an effect on the spectrum of the hy- 

 drogen similar to that change which is observed in the spec- 

 trum of the chromosphere when Ave pass from its lower to 

 its upper limit. The mean height of the chromosphere, on 

 the most quiet portion of the sun's surface, is about ten sec- 

 onds of an arc. Combining this with the j^receding datum 

 of Wullner, Zullner says that the absolute temperature of 

 the chromosphere is 61,350 degrees Centigrade. To this re- 

 sult Zollner attributes, naturally, only very slight weight, 

 except in tliat it must be considered an approximation suffi- 

 ciently near to the truth to show that the very high temper- 

 ature of 5,000,000 advocated by Secchi is entirely out of the 

 question. Secchi had established his very high temperature 

 upon the assumption of the proportionality between the radi- 

 ation of heat from any body and its absolute temperature. 

 This assumption, however, has already been shown by Zoll- 

 ner to be quite erroneous ; and, lately, Soret has, by some 

 interesting investigations, confirmed the correctness of Zoll- 

 ner's conclusions. Soret, by means of a very hot flame, brings 

 to a bright glow a plate of zircon, and then determines its 



