Some Contemporary Advances in Physics VIII 

 The Atom-Model, First Part 



By KARL K. DARROW 

 A. lMK(ii)r( roKV KiMAkKs Audi r Atom-Mohi-is 



MOKK than .iii> otluT word ol ilu- I.iiijjiiagc, tlu- word atom 

 is iinplir.ited with the histors- of human sporuUitions con- 

 ivrning the nature of things. It is intnKiuced wlien people cease to 

 content themselves with obser\ing, and begin to philosophize. There 

 are man>' of the fundamental and essential writings of the literature of 

 physics in which it does not appear, or appears without warrant. 

 These are the descriptions of things observed, the accounts of experi- 

 ments, the records of measurements, on which the edifice of theoretical 

 physics is founded. There are many articles of what is commonly 

 called the "theoretical" sort in which it does not occur. Such are the 

 pafX'rs on the motions of planets, on the vibrations of elastic solids, 

 on the currents in electrical networks, on the courses of light-rays 

 through optical systems — papers which are essentially descriptions, 

 although they give the impression of being something greater and 

 deeper because they relate to idealized cases, and are phrased in the 

 laconic language of mathematics. When the word atom appears 

 justifiably in a discourse, it means that the author has departed from 

 the safe routine of describing observed and obser\able events, how- 

 ever selectively, however skilfulK', however intelligently. It signifies 

 that he has gone beyond the limits of obser\ation, and has entered 

 upon the audacious adventure of constructing by the side of the real 

 universe an ideal one, which shall act as the real one does, and be 

 intelligible through and through. 



Atoms are the building stones of this art-world or image-world, 

 which is intended to represent the actual world, imperfectly indeed 

 for the time being, perhaps completely at some distant day. Some 

 few experiments, it is true, prove (as well as anything can prove any- 

 thing else) the existence of very minute particles of matter ha\'ing the 

 minute charges, the minute masses, the minute magnetic moments 



' This part, the first of two composing the article, is devoted chiefly to the facts 

 of observation which the favorite atom-model of the physicists of toda> — the atom- 

 model known by the names of Rutherford and of Bohr — is designed to interpret. 

 .■\ brief description of this atom-model is included: but the detailed account of the 

 peculiar features, of the strange ajid important limitations which are imposed upon 

 it to adjust it to all the phenomena mentioned, is reserved for the second part. 

 Owing to the great quantity of information which it is desirable to present, the 

 article needs all the Ijcnefit it can derive from a careful and obvious organization, 

 and I have sacrificed fluency to a quite formal arrangement under headings and 

 sub- headings. 



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