INORGANIC EVOLUTION. 207 



the evolution of living things is not parallel to, but the con- 

 tinuation and end of, the inorganic evolution. We deem that 

 the governor of this inorganic evolution is temperature, and 

 that the evolution itself results from a running down of 

 temperature. Before proceeding to the evidence for this 

 statement we must first present the basis upon which rests 

 the whole building of Lockyer's proof. Before speaking of 

 "hottest suns" and "cooler suns" we must have some sys- 

 tem of celestial thermometry by which we may compare 

 beyond peradventure their relative temperatures. The 

 basis upon which this rests is strong and simple. We know 

 from actual observation that on heating an iron rod, let us 

 say, it first becomes red hot and then proceeds gradually 

 up to whiteness. Now, if we examine with a spectroscope 

 the light from the rod in its progression to white heat, we 

 find first that only the red end of the spectrum is seen; on 

 further heating, the orange and yellow portions of the spec- 

 trum appear and, finally, at a white heat, we have the 

 whole visible spectrum from red to violet. Not only so, 

 but by the aid of photography we discover that as the rod 

 grows still hotter the spectrum proceeds farther and farther 

 into the invisible portion of the spectrum beyond the violet. 

 We can, thus, make this general statement, that the hotter 

 a body is the more does its spectrum lengthen out, the more 

 does it extend from red into the ultra violet, and this is as 

 true of a star as a poker. 

 Lockyer first divides the stars into three main groups: 



Gaseous stars Longest Spectrum. 



Metallic stars Medium Spectrum. 



Carbon stars Shortest Spectrum. 



And on the basis of the foregoing fact he draws the following 

 deduction: 



