SCIENCE 



NOV 6- 1917 



Fridat, November 2, 1917 



CONTENTS 



The Structure of Atoms, and the Evolution of 

 the Elements as related to the Composition 

 of the Nuclei of Atoms: Professor Will- 

 iam D. Harkins 419 



Scientific Events: — 



Chemicals and War in England; Faculty 

 Changes at the Massachusetts Institute of 

 Technology; The University of Pittsburgh 

 and the Army Medical Service; The War 

 and Navy Departments and the Coast and 

 Geodetic Survey 427 



Scientific Notes and News 330 



University and Educational News 432 



Discussion and. Correspondence : — 

 - Algonlcian Bacteria and Popular Science: 

 De. Henry Faiepield Osborn. The Teach- 

 ing of Optics: Dr. David Vance Guthrie. 

 Trans-Pacific Agriculture : Dr. 0. F. CoOK. 

 Benjamin FranJclin and the Struggle for 

 Existence : Professor B. W. Kunkel .... 432 



Scientific Books: — 

 Lunge on the Manufacture of Sulphuric 

 Acid: Professor Jas. Lewis Howe. An 

 Encyclopedia of Peaches: F. A. W 438 



Special Articles: — 



Comparison of the Catalase Content of the 

 Breast Muscle of Wild Pigeons and of Ban- 

 tam Chicktnt: W. E. Buroe. Cilia in the 

 Arthropeda: Dr. Nathan Fasten. Phyth- 

 mic Banding : Dr. Harry N. Holmes .... |40 



MSS. intended for publication and books, etc., intended for 

 review should be sent to The Editor of Science, Garrison-on- 

 Hudson, N. y. 



THE STRUCTURE OF ATOMS, AND THE 

 EVOLUTION OF THE ELEMENTS AS 

 RELATED TO THE COMPOSI- 

 TION OF THE NUCLEI 

 OF ATOMS 1 

 The general theory of the structure of 

 the atom which seems to be most closely in 

 harmony with the facts is that developed 

 by Rutherford. His theory assumes that 

 the atom consists of a central nucleus or 

 sun, and that the satellites of the miniature 

 solar system are the negative electrons. 

 The central nucleus is supposed to contain 

 almost all of the mass of the atom, and is 

 charged with positive electricity. That 

 this nucleus is very minute in comparison 

 with the size of the atom is indicated bj;- 

 the work of Rutherford, of Geiger and 

 Marsden, and of Darwin, who find that the 

 deflection of alpha particles, which are shot 

 from radioactive atoms at speeds which 

 approach 20,000 miles per second and so 

 pass directly through other atoms, is of 

 such a character as to indicate that the 

 positive charge of the atom is very highly 

 concentrated. Thus Darwin's work indi- 

 cates that the maximum diameter of the 

 nucleus of a hydrogen atom (1.7 X 10"" 

 cm.) is only about one-one hundred thou- 

 sandth of the diameter usually assumed for 

 the atom. On this basis the atom would 

 have a volume a million-billion times larger 

 than that of its nucleus, and thus the nu- 

 cleus of the atom is much smaller in com- 



■ 1 Address presented at the Symposuim on the 

 Structure of Matter at the New York meeting of 

 the American Association for the Advancement of 

 Science. A bibliography will be found in the fol- 

 lowing papers: Jour. American Chemical Society, 

 37, 1367-1421 (1915), 39, 856-879 (1917); Philo- 

 sophical Magazine, 30, 723-734 (1915). 



