56 Prof. W. A. Norton on the Physical Cons tiiidivn of the Eu 



ously visible in total eclipses, and observable at all times with 

 the aid of a spectroscope, are most of them due to violent erup- 

 tions of masses of incandescent hydrogen*. He remarks that 

 " it is impossible, without passing beyond the well-known ana- 

 logies necessary for the explanation of cosmical phenomena, to 

 assign any other cause to these eruptions than the difference of 

 pressure of the gases emanating from the interior and from the 

 surface of the sun. To make such a difference of pressure pos- 

 sible, it is necessary to admit the existence of a separating stra- 

 tum between the inner and outer strata of hydrogen, the latter 

 of which, as is well known, forms an important portion of the 

 solar atmosphere. In reference to the physical constitution of 

 this stratum, we must furthermore assume that it cannot be 

 gaseous, and must therefore be either solid or liquid." He re- 

 marks further that "with regard to the inner masses of hydrogen 

 bounded by that stratum two suppositions are possible, viz. : — (1) 

 The whole interior of the sun is filled with incandescent hydro- 

 gen gas, which would make the sun an immense bubble of hy- 

 drogen surrounded by a liquid glowing envelope. (2) The masses 

 of hydrogen bursting out into protuberances are local collections 

 in bubble-like caverns, which form in the superficial layers of a 

 liquid glowing mass and burst through when the pressure of the 

 confined gas increases." Professor Zollner adopts the latter 

 supposition as the more probable of the two. 



This theory may furnish an adequate supposable cause for the 

 observed eruption of incandescent masses of hydrogen ; but its 

 fundamental hypotheses have no secure ground to rest upon. 

 The notion that the sun's photosphere is in the liquid state is 

 irreconcilable with the astonishing rapidity with which changes 

 often occur on the sun's surface, and also with the fact that the 

 vast elevated masses, seen as the faculse, occasionally retain the 

 same position for several days — and though suggested long since, 

 has not, to my knowledge, been adopted by any astronomical 

 observer. No hypothesis of the possible origin of the sun's 

 spots upon this idea has been framed that affords a satisfactory 

 explanation of even their more conspicuous features and pheno- 

 mena. To this remark the theory advanced by Professor Zollner, 

 viz. that t( the nucleus of the solar spots is a scoriaceous pro- 

 duct of local cooling on a liquid surface, and the penumbrse 

 clouds of condensation which surround at a certain height the 

 coasts of these islands of slag," offers no exception. It is not 

 new, and has been already overthrown by the investigations of 

 M. Fayef. The other fundamental hypothesis of Professor 



* Philosophical Magazine, Nov. 1 S/0. 

 t Comptes Rendns. vol. Ixi. p, 1089. 



