TO Scientific Intelligence. 



metic series 1, 2, 3, 4, and the effective areas are in the ratios 

 1 : 2 2 : 3 2 : 4 2 : That each shell is divided into cellular spaces or 

 cells occupying equal areas : That the first shell contains 2 cells, 

 the second 8, the third 18, and the fourth 32 : That each of the 

 cells in the first shell can contain only one electron, but each 

 other cell can contain either 1 or 2 : That all of the inner cells 

 must have their full quota of electrons before the outside shell 

 can contain any: That no cell in the outside layer can contain 

 two electrons until all the other cells in this layer contain at 

 least one. 



It appears that this theory of atomic structure not only 

 explains in a satisfactory manner the general properties and 

 relationships of all the elements, but also gives a theory of the 

 formation and structure of compounds which agrees excellently 

 with the facts. — Jour. Amer. Chem. Soc, 41, 868. 



h. l. w. 



2. Qualitative Chemical Analysis; by "Wilfred "Welday 

 Scott. 12mo, pp. 350. New York, 1918 (D. VanNostrand 

 Company. Price $2.50 net). — This is the third edition, com- 

 pletely revised and enlarged, of an unusually extensive text book 

 on qualitative analysis. One of the satisfactory modifications of 

 this last edition is the introduction of a large number of chemical 

 equations for the purpose of explaining the reactions. The book 

 is essentially a laboratory guide with extensive directions for 

 the work of students, but it gives much also in the way of expla- 

 nations, notes and systematic questions for class-room use. 

 There are many tables explaining analytical operations, showing 

 the reaction of metals and acids, the properties of inorganic com- 

 pounds, etc. 



The book is an impressive one from the very large amount of 

 information that it presents, and for the generally excellent 

 manner of presentation. Perhaps the course that is given may 

 be considered too elaborate for many classes of beginners, but it 

 must be admitted that it is easier to omit portions of an exten- 

 sive text book than to supply deficiencies with one that is too 

 short. There is room in many cases for differences of opinion in 

 regard to the selection of analytical methods, but it may be said 

 that in the book under consideration several methods of detection 

 or separation are frequently described, and that the methods are 

 generally well chosen. h. l. w. 



3. The Origin of Spectra. — In a recent theoretical paper by 

 J. J. Thomson an explanation of the origin of spectra is given 

 which leads to results of the right kind and which is very helpful 

 in forming a mental picture of the processes of radiation. Of 

 course, the author does not claim that his point of view is the 

 only correct one, on the contrary he points out the possibility of 

 an infinite number of laws of force each of which would 

 account for the observed facts and not conflict with well estab- 

 lished electrodynamical principles. 



