THE WORLD BEFORE LIFE. 515 



phases of growth had all been completed, and we should have passed 

 beyond the period of organic activity. The New-Zealander would 

 have leaped over the ruins of London, and the "last man" of Ho- 

 garth would have .finished gazing upon the ruins of intellectual ac- 

 tivity. 



Fio. 2. 



Spiral Nebula in Canes Venatici (H., 1622). 



Cosmical Analogies. — Space is full of bodies resembling our earth 

 in all stages of its growth. The earlier stages are displayed in nebulae, 

 comets, and suns. The former, by the improved methods of modern 

 investigation, are clearly shown to be in a gaseous condition, intensely 

 heated, though not so hot as the sun, and so tenuous that the bright- 

 ness of the stars behind is hardly dimmed. 



There has been great progress in the study of the nebulae. Many 

 had been resolved into clusters of small stars by the more powerful 

 instruments of recent manufacture, so that astronomers doubted the 

 existence of any unresolvable forms. But, in 1866, Mr. William Hug- 

 gins showed that nineteen out of the sixty nebulae seen through the 

 great reflecting telescope of the Earl of Rosse presented spectra ex- 

 hibiting the bright bands indicative of heated luminous gas. Hence 

 the world could no longer doubt the settlement of the question whether 

 any of the nebulae are composed of vapors. Prof. Young says that 

 the majority of the nearly 8,000 known nebulae are luminous clouds of 

 heated gas, with minute solid and liquid particles scattered through 

 them. In a recent number of The Popular Science Monthly, Mr. 

 F. W. Clarke has classified these bodies, suggesting that ther6 may 

 be a law of development among them. The most distinct are com- 

 posed of nitrogen and hydrogen, possessing a temperature beneath 

 that of the sun. He propounds the hypothesis whether nebulae may 

 not pass by degrees into suns, the sixteen elements known to exist in 



