376 THE PJDDLE OF THE UNIVERSE. 



century. Yet here again it had the honour of open- 

 ing out entirely new paths and infinitely enlarging 

 our outlook on the universe. The invention of photo- 

 graphy and photometry, and especially of spectrum 

 analysis (in 1860 by Bunsen and Kirchoff), introduced 

 physics and chemistry into astronomy and led to 

 cosmological conclusions of the utmost importance. 

 It was now made perfectly clear that matter is the 

 same throughout the universe, and that its physical 

 and chemical properties in the most distant stars do 

 not differ from those of the earth under our feet. 



The monistic conviction, which we thus arrived at, 

 of the physical and chemical unity of the entire cosmos 

 is certainly one of the most valuable general truths 

 which we owe to astrophysics, the new branch of 

 astronomy which is honourably associated with the 

 name of Friedrich Zollner. Not less important is the 

 clear knowledge we have obtained that the same laws 

 of mechanical development which we have on the earth 

 rule throughout the infinite universe. A vast, all- 

 embracing metamorphosis goes on continuously in all 

 parts of the universe, just as it is found in the 

 geological history of the earth ; it can be traced in 

 the evolution of its living inhabitants as surely as in 

 the history of peoples or in the life of each human 

 individual. In one part of space we perceive, with 

 the aid of our best telescopes, vast nebulae of glowing, 

 infinitely attenuated gas ; we see in them the embryos 

 of heavenly bodies, billions of miles away, in the first 

 stage of their development. In some of these " stellar 

 embryos " the chemical elements do not seem to be 

 differentiated yet, but still to be buried in the homoge- 

 neous primitive matter (proikyl) at an enormous tempe- 

 rature (calculated to run into millions of degrees) ; it is 



