Solar Olid Flanetarij Evolution. 



57 



and gravitation, those arch-mechanics, which without the 

 aid of saw or hammer have builded the universe, contended 

 for mastery in the evolution of the earth just as they did in 

 our puff of steam. Gravitation has always prevailed in the 

 end, because gravitation cannot leak away like heat. The 

 «arth was first a nebula — perhaps an invisible gas — then 

 in the state of a liquid, and finally it became, as we see it, 

 solid, cool and habitable. It is only a question of the 



Fig. 2,— representing the ring liroken into several segments. 



amount and intensity of heat, (riven heat enough and it 

 would be as easy to turn the eartli into a nebulous cloud as 

 to melt a snow-iiake. 



Tja])lace gives us one hypothesis of the origin of the so- 

 lar system, which I will endeavor to illustrate. (At this 

 ])oint the lights in the church were extinguished, and a pic- 

 ture of a revolving nebula was thrown upon the screen. 



