F W. Very — A Cosmic Cycle. 55 



and this will produce spectral differences according to the level 

 of the absorption ; but the spectral differences to which Lock- 

 yer refers are of another sort and favor the interpretation that 

 there has been a breaking down of the more complex atoms 

 and an increase of simpler atoms, either relatively by the dis- 

 appearance of the more complex, or possibly by a transforma- 

 tion of the complex into simpler forms. If we suppose that 

 those atoms having large atomic weights have been formed by 

 the expenditure of a greater energy, or that their latent heat 

 of formation is relatively very great, the transformation of 

 heavy atoms into lighter ones will set free an amount of energy 

 equivalent to the difference in the heat of formation ;* but 

 whether produced by transformation or destruction of atoms, 

 the setting free of latent heat of atomic formation ought by 

 analogy to develop relatively larger amounts of heat, or of 

 energy to use a more elastic term, than transformations in the 

 more compounded states of matter; and this development of 

 energy may increase with rising temperature and excessive 

 condensation, until limited in another way ; for since the pres- 

 sures produced by gravitation must be greater in very large 

 masses, it is probable that the explosive energy developed by 

 atomic transformation will increase as a complex function of 

 the mass and its condensation ; and thus explosive energy 

 may be so great as to rupture the mass when this exceeds a 

 certain size and degree of condensation. Star clusters may 

 have resulted from such cataclysms in stars of very great mass.* 

 So many of the spiral nebulae consist of similar curved arms 

 emanating in opposite directions from a common center, that 

 we seem driven to admit the existence of directed explosive 

 forces of enormous magnitude. 



On June 26, 1885, at l h 25 m Paris mean time, Trouvelotf 

 saw two prominences of extraordinary height at opposite 

 extremities of a solar diameter (position angles, 59° and 239°). 

 The eastern prominence measured 10/5, or about a third of 

 the solar diameter, and the other was nearly as large. The 

 western prominence, which was observed in its active stage, is 

 thus described : " Its aspect was tree-shaped, and from its base, 

 which resembled the root of a Pan claims, rose a slightly wavy 

 column, 5' high, perpendicular to the surface, and ramifying 

 into numerous branches which diminished in brilliancy as they 

 rose, for the most part becoming invisible before their summits 



* It will be noticed that the meaning of the term "heat of formation" is 

 extended beyond its usual application ; but since heat is understood to be the 

 energy of motion of the invisible constituents of bodies, it is appropriate enough to 

 apply the same form of speech to the corresponding activity of the atomic con- 

 stitnents. 



\ . E L. Trouvelot. '"Remarquables protuberances solaire diametralement 

 opposees.' 1 L'Astronomie, vol. iv, p. 441, 1885. 



