508 



SCIENCE 



[N. S. Vol. LI. No. 1325 



ently conflicting theories. The purpose of 

 this paper is to show that these contributions 

 not only do not conflict, but that all of them 

 are essential parts of a picture, which is 

 nearer completion than most of us realize. 

 The main contributions may be summarized 

 as follows: 



Eitz showed that by assuming the nucleus 

 to be magnetic, so that the force determining 

 the vibration of the electron depends on the 

 velocity instead of the position of the electron, 

 one obtains a frequency law involving only 

 the first power of the frequency, in accordance 

 with observations. 



The essential part of Bohr's beautiful 

 theory is the mechanism by wliich he accounts 

 for Ritz's combination principle namely, that 

 the frequency of radiation depends not on 

 where the electron is, or where it came from, 

 but upon both. 



J. J. Thomson added the idea that Bohr's 

 stable orbits, and the quantum relations con- 

 nected with them, are due to a skeleton struc- 

 ture of the nucleus and not to any discon- 

 tinuity of energy. 



Sommerfeld extended Bohr's theory to 

 atoms of higher atomic weight, and has drawn 

 a beautiful picture. His main contribution is 

 the idea that the orbit may be either a circle 

 or an ellipse of definite eccentricity, which 

 accounts with extreme precision for the sep- 

 aration of doublets both in X-ray spectra and 

 the hydrogen spectrum. 



Langmuir showed that all known chemical 

 properties are satisfied by an atom with rela- 

 tively stationary electrons, arranged in con- 

 centric shells about the nucleus. 



~By combining these contributions, namely, 

 the magnetic nucleus of Ritz, Bohr's stable 

 orbits, Thomson's skeleton nucleus, Sommer- 

 feld's elliptical orbits, and Langmuir's sta- 

 tionary electrons, we arrive at a composite 

 picture which represents our present knowl- 

 edge remarkably well. The rotating point 

 electron is replaced by a ring-shaped electron. 

 The constant angular momentum of the 

 rotating electron is replaced by constant 

 magnetic moment of the ring. In the case of 

 hydrogen and ionized helium the ring sur- 



rounds the nucleus, and the picture is iden- 

 tical with Bohr's. In the ease of the other 

 elements the rings lie on the surface of con- 

 centric shells, in positions corresponding to 

 Langmuir's cells. The condition of constant 

 angular momentum of each ring electron 

 holds for all atoms, and Sommerfeld's picture 

 of the circular and elliptical rings is applied 

 to the shape of the ring electron. 



The discussion following the symposium 

 was of necessity brief. Emphasis was given to 

 the clear advantage of preferring a theory of 

 atomic structure that gives correct quantita- 

 tive results. G. W. Stewart, 



Secretary Section B 



SCIENTIFIC EVENTS 



PUBLICATIONS AND MEMBERSHIP OF THE 

 NATIONAL ACADEMY OF SCIENCES 



At the recent meeting of the academy the 

 home secretary presented the following report : 



The President of the National Academy op 

 Sciences. 



Sir: I have the honor to present the following 

 report on the publications and membership of the 

 National Academy of Sciences for the year ending 

 April 26, 1920. 



Two parts of Volume 14 of the Memoirs of the 

 National Academy of Sciences have been completed 

 and dlistributed : the second memoir, ' ' Complete 

 Classification of Triad Systems," by H. S. White, 



F. N. Cole and L. D. Oummings, and the fourth 

 memoir, "Minor ConS'tituents of Meteorites," by 



G. P. MerriU. 



The third memoir, "Tables of Minor Planets," 

 by A. O. Leuschner, A. E. Glancy, and S. H. Levy, 

 and the fifth and final memoir of Volume 14, 

 "Tables of the Exponential Function," by C. E. 

 Van Orstrand, are now in page proof and will be 

 issued shortly, as will also Volume 15, ' ' Psycholog- 

 ical Examining in the United States Army," by 

 Robert M. Yerkes. 



Volume 16, first memoir, ' ' Lower California and 

 its Natural Resources," by E. W. Nelson, and the 

 second memoir, "Studies upon the Life Cycles of 

 Bacteria, " by F. Lohnis, axe now in galley proof. 

 The third memoir, "A Recalculation of Atomic 

 Weights," by F. W. Clarke, is now in the hands of 

 the printer. 



Volume VIII. of the Biographical Memoirs has 

 been completed with the publication of the biog- 



