F. W. Very— A Cosmic Cycle. 185 



Art. XVI.— A Cosmic Cycle ; by Frank W. Very. 



[Concluded from page 114.] 

 Concluding Stages of Stellar Groicth. 



I have referred the gradual diminution of hydrogen after 

 the Sirian stage to its being used up in the formation of planets 

 and comets. To this cause is adjoined in the stars of Secchi's 

 fourth type, the attainment of a temperature so low that 

 hydrogen and carbon combine, whereby the last traces of 

 hydrogen are removed. Previously to this, however, come 

 bright-line variable stars of banded type, where either the 

 evolution of hot hydrogen proceeds intermittently from a 

 viscid interior, or else fresh hydrogen is added from time to 

 time by external meteoric accessions. 



The bright-line, long-period variables of Secchi's third type 

 are connected by their spectra with the last stages of the solar 

 type. I interpret them in this way: As condensation pro- 

 gresses towards its last degree, consistent with the maintenance 

 of stellar functions, central heat becomes excessive, while it is 

 more and more difficult for inner hot material to be transferred 

 to the surface, because viscosity is so great as to be the pre- 

 cursor of final solidification. Under these circumstances, there 

 is a recrudescence of explosive power. Central explosions, no 

 longer of sufficient strength to disrupt the body as at the end 

 of the Orion era, are nevertheless strong enough to break 

 through the dense substance of the sphere, casting up above 

 the heavy metallic vapors which rest upon the cooling photo- 

 sphere, prominences of enormous size and of vivid luminosity. 

 Chromospheric radiation begins to approach that of the pho- 

 tosphere in intensity. Lockyer* has rejected the supposition 

 as to " gigantic supra photospheric atmospheres " in these stars 

 in favor of a primitive meteor-swarm theory, but without con- 

 sidering the undoubted affinities with the solar type. 



The formation of a vast hydrocarbon atmosphere is the most 

 important characteristic of the last stage of stellar evolution, 

 constituting Secchi's fourth type. The cessation of hydrogen 

 eruptions and the spectral change to dark hydrocarbon flutings 

 appears to be sudden, since there are no intermediates, and 

 perhaps coincides with central solidification and absence of 

 further central explosions. 



It would be interesting to inquire how far the change of 

 electrification from the negative hydrogen spectrum of solar 

 and earlier stars, to the positive hydrogen spectrum in the 

 banded variables, may have been brought about by explosions ; 

 for it is hardly possible that the enormous electric charges con- 



* The Meteoritic Hypothesis, p. 352, et seq. 



