FITNESS 9 



a system of materials out of which the uni- 

 verse is formed, within which all chemical 

 changes (except certain phenomena of radium 

 and a few other anomalies, including perhaps 

 unknown changes in the interiors of the 

 celestial bodies) take place. 



It is certain that nearly all the chemical 

 transformations upon the earth consist of 

 rearrangements of the atoms of the known 

 elements. A century and a half of scientific 

 chemistry guarantee that conclusion with a 

 security rarely attained in descriptive science. 

 And the testimony of the spectroscope is 

 equally conclusive that the visible stars, 

 like the sun itself, are made up almost or 

 quite exclusively of the same chemical ele- 

 ments. Such facts, so familiar that they re- 

 quire no comment or explanation, might 

 sufficiently justify the acceptance of the chem- 

 ist's known elements as the only important 

 matter in the universe. But even more 

 weighty evidence is at hand ; I mean the 

 so-called periodic classification of the ele- 

 ments. 



It has long been evident that simple rela- 

 tionships exist in some cases between the 

 atomic weights of similar elements. For ex- 

 ample, the atomic weights of bromine, stron- 

 tium, and selenium are approximately equal 



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