PROCEEDINGS OF THE ACADEMY AND AFFILIATED 



SOCIETIES 



THE PHILOSOPHICAL SOCIETY OF WASHINGTON 



The 775th meeting was held on May 27, 1916, at the Cosmos Club. 

 President Briggs in the chair; 47 persons present. The minutes of 

 the 774th meeting were read in abstract and approved. 



The evening was devoted to a symposium on the atom. Mr. H. L. 

 Curtis presented a paper on The atom as a miniature solar system. 

 The author briefly sketched the history of atomic theory from Dalton's 

 work in 1803 to the recent work of J. J. Thomson, Rutherford, Nichol- 

 son, Bohr, Van der Brock, Zeeman, and others. Two types of nucleus 

 atom are possible, viz, the planetary type and the Saturnian type. 

 In the planetary type each electron has an orbit different from that of 

 any other electron, as is the case of the planets rotating about the 

 sun, but different from this in that they repel each other while the 

 planets attract. In the Saturnian type, which is most generally ac- 

 cepted, the electrons rotate in rings around the nucleus. Bohr's 

 assumptions of the laws holding at atomic dimensions and the results 

 from his hypothesis were given in detail. The present trend of thought 

 is towards accepting the Saturnian type of the nuclear atom. It is 

 generally conceded that the forces which bind the parts of the atom 

 together are different from those with which we are accustomed' to 

 deal. The radiation giving the lines of the visible spectrum is con- 

 cerned with the outer rings of the atomic system, while X-rays are 

 produced by vibrations of the inner rings of electrons. Radioactive 

 phenomena and chemical affinity appear to be concerned with the 

 nucleus. 



Discussion. Mr. Agnew referred to experiments in magnetization 

 which indicate the validity of the Saturnian or planetary-type theory. 

 Bohr's theory predicted that certain lines of the spectrum of helium 

 were due to hydrogen. Mr. Bauer referred to the looseness of terms 

 found in writings on the atomic theories; for example, 8 out of 10 

 will use "rotation" instead of "revolution." In many theories of 

 astronomy it is not necessary to take account of rotation, but no 

 astronomer would attempt to explain all facts and phenomena only 

 by revolution; it, therefore, appears that the time may come when it 

 may be necessary to consider both rotation and revolution in connec- 

 tion with atomic theories. Mr. Sosman referred to the recent work 

 on the valence of atoms in chemical compounds. Mr. Wright re- 

 ferred to studies in crystal structure in which particular directions 

 within an atom find expression in atomic arrangement of crystals. 



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