JOURNAL 



OF THE 



WASHINGTON ACADEMY OF SCIENCES 



Vol. U Jin.Y 19, 1921 No. 13 



CHEMISTRY. — The evolution of matter ^ Frank WigglESWORTh 

 Clarke, U. S. Geological Survey. 



During the greater part of the nineteenth century many philosophi- 

 cal chemists held a vague behef that the so-called chemical elements 

 were not distinct entities, but manifestations of one primal form of mat- 

 ter, the proiyle, as it was sometimes termed. Other chemists, more con- 

 servative, looked askance at all such speculations, and held fast to what 

 they regarded as estabHshed facts. To them an element was something 

 distinct from all other kinds of matter, a substance which could neither 

 be decomposed nor transmuted into anything else. One fact, how- 

 ever, they ignored, namely, that the elements were intimately con- 

 nected by many relations, which are best shown in the periodic law of 

 Mendeleeff, who actually predicted the existence of unknown elements 

 which were afterwards discovered. This is ancient history, with which 

 all chemists are now familiar. It became evident to most chemists 

 that the elements must have had some community of origin, for other- 

 wise their relations to one another are unintelligible. 



In 1873 I ventured to publish the suggestion, ^ based on spectro- 

 scopic evidence and assuming the nebular hypothesis to be true, that 

 the evolution of planets from nebulae had been accompanied by an 

 evolution of the chemical elements. The nebulae are chemically 

 simple, the hotter stars more complex, the cooler stars and the Sun 

 still more so, and the solid Earth the most complicated of all. This 

 was promptly denounced as heresy ; but nearly a year later Lockyer' 

 put forth an analogous suggestion, based upon the same sort of evi- 

 dence, but starting from the other end. That is, he assumed that in 

 the hotter stars some elements were dissociated, and his suggestion 

 was received with a good deal of favor. The heresy was beginning to 

 be orthodox. In course of time the discovery of radioactivity by 

 aecquerel and of radium by Madame Curie established the fact that 



> Published with the permission of the Director, U. S. Geological Survey. Received 

 June 16, 1921. 



*F. W. Clarke, Evolution and the spectroscope. Pop. Sci. Mon. January, 1873. 

 3N. LocKVER, Proc. Roy. Soc. 21: 513. (Paper dated Nov. 20, 1873). 



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