A WEEKLY ILLUSTRATED JOURNAL OF SCIENCE. 



" Y'o the solid ground 

 Of Nature trusts the mind which builds for aye." — Wordsworth. 



SATURDAY, JULY 7, 1923. 

 CONTENTS. 



Modern Physics and the Atom .... 



The Conquest of Malaria. By Colonel W. G. King 



Variable Stars. By H. C. P 



The Study of Fossils. By A. S. W. 



Our Bookshelf ........ 



Letters to the Editor : — 



Positive Ray Analysis of Copper. — Prof. A. J. 

 Denpster ....... 



Expansion of the Wings of Lepidoptera after Emerg- 

 ence from the Chrysalis. ( Illustrated. ) — A. Mallock, 



F.R.S 



The Formation of New Egg Cells during Sexual 



Maturity. ( Illustrated. ) — Prof. J. Bronte Gatenby 



Origin of certain Filamentous Forms from Eocene 



Beds. — W. N. Edwards ..... 



Hafnium and Celtium. — Prof. Harold S. King 



Distribution of Limncea pereger and L. truncal ula. — 



Miss Kathleen E. Carpenter .... 



Scientific Names of Greek Derivation. — Dr. John W. 



Evans, F.R.S.,; Prof. Grenville A. J. Cole, 



F.R.S 



On the Significance of "Rings" on the Shells of 



Cardium and other Molluscs. — Dr. J. H. Orton . 



A Crystallisation Phenomenon. {Illustrated.) — 



C. R. Bailey 



Studies from a Wireless Laboratory. ( With Diagrams. ) 



By Prof. W. H. Eccles, F.R.S 



Ur of the Chaldees. {Illustrated.) — By C. Leonard 

 WooUey ........ 



Current Topics and Events ..... 



Our Astronomical Column 



Research Items ....... 



The Pasteur Centenary Celebrations. By Prof. 



George H. F. Nuttall, F.R.S 



Cambridge Meeting of the International Union for 

 Pure and Applied Chemistry .... 



Tercentenary of the Oxford Botanic Garden 

 University and Educational Intelligence . 

 Societies and Academies ..... 



Official Publications Received 



Diary of Societies 



The Structure of the Atom. (Illustrated.) By Prof. 

 N. Bohr 



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Modern Physics and the Atom. 



IN another part of this issue we pubhsh as a special 

 supplement a translation of Prof. N. Bohr's 

 lecture on atomic structure, which was delivered at 

 Stockholm last December on the occasion of receiving 

 the Nobel prize for physics. It seems a fitting occasion 

 to survey the general lines of the recent development 

 of physical theories as to the nature of the atom. 

 The views put forward in Prof. Bohr's address may 

 fairly be regarded as the furthest stage yet reached. 



The leading feature of the physics of the twentieth 

 century has been the development of our present 

 concrete picture of the individual atom. In this 

 respect modern physics stands rightly in sharp 

 contrast with previous work — properties of matter in 

 bulk, thermodynamic, electrodynamic, and optical 

 theory. These theories formed the main part of the 

 studies and contributions of physicists before 1900, 

 and advanced with particular rapidity in the latter 

 half of the last century. In all this work, though the 

 atomic nature of matter had already come to general 

 recognition in virtue perhaps of chemical rather than 

 physical evidence, atoms, if recognised at all, play 

 only a secondary part. The reason is that though 

 theories of matter {e.g. gases) may be built up on an 

 atomic basis, applications of these theories are always 

 statistical ; in making them an averaging process is 

 used, and the particular features of an atomic model 

 largely disappear. For example, almost any atomic 

 model will reproduce the main properties of a gas. 

 It is only in the finer points such as the exact variation 

 of viscosity with temperature that the particular form 

 of atomic model becomes relevant, and even here the 

 variation deduced is very insensitive to the model 

 chosen. Crude and vague ideas of the atom — little 

 more than the mere recognition of its existence — were 

 all that were necessary to physics in this phase. 



NO. 2801, VOL. I 12] 



