REVIEWS 483 



apparatus and tabulated details of their results. Some of the articles contain 

 useful practical bints and a bibliography ; but more often the latter is re- 

 placed by the less satisfactory system of scattered footnote references. The 

 diagrams and illustrations are very numerous, though sometimes on rather 

 too small a scale to be really useful {i.e. usable without reference to the 

 original paper) . In a few cases descriptions of apparatus have been omitted 

 in favour of a more extended discussion of results. It is obvious that the 

 articles are too numerous and lengthy to permit of anything but the most 

 general description and criticism. Some of the more noteworthy articles 

 in Vol. I have already been indicated. Others which ought also to be men- 

 tioned include those on Thermal Expansion (A. W. Porter) ; Thermodynamics 

 (Ewing) ; and Pyrometry (Griffiths) ; together with others on various engin- 

 eering matters such as Elastic Constants (R. G. Batson), Balancing of Prime 

 Movers (Dalby), etc. 



Vol. II, on Electricity, will be found to be of even greater value to the 

 average physicist than Vol. I. Among its outstanding features are Albert 

 Campbell's contributions on Electrical Capacity and Inductance. These 

 contain many detailed practical hints in addition to descriptions of all the 

 recognised methods of measurement and of the special apparatus required 

 in using them. Similar remarks apply to F. E. Smith's articles on Resistance 

 and Systems of Electrical Measurement, which contain accounts of the latest 

 methods of absolute measurement, and for the setting up of copies of the Inter- 

 national Standards. Magnetism is treated very fully from both the practical 

 and theoretical standpoints in articles by Chapman, Chree, Honda, Taylor 

 Jones, Oxley, etc., and the latest developments in thermionics are covered 

 by O. W. Richardson and C. L. Fortescue. The engineering side is not so 

 prominent here as in Vol. I, but the physicist will find all he wants in such 

 articles as those on Dynamo Electric Machinery, Wattmeters, Transformers, 

 and, of course. Telegraphy and Telephony. 



The manner in which the Dictionary is produced is admirable ; the only 

 practicable improvement which suggests itself is that the numbers and headings 

 of the paragraphs should have been printed in heavier type : they are not 

 now as readily distinguishable as they might have been in the interests of 

 quick reference. The editor's task in the selection of articles and distribu- 

 tion of space must have been heavy and difficult ; he has accomplished it 

 with notable fairness and success. The cost of the volumes is considerable, 

 but quite reasonable in view of the quantity and quality of their contents. 

 Those whose library of physics books has yet to be formed will find its size 

 and cost greatly diminished by the inclusion of the Dictionary. It will 

 prove indispensable in all laboratories whether devoted to teaching, research, 

 or the routine of industry ; as a time saver it will be invaluable to all engaged 

 in lecturing on the subject, and the writers of our future textbooks will find 

 it a mine of extraordinary richness. The publishers are to be congratulated 

 on their enterprise, and on the addition of yet another item to their already 

 long catalogue of science classics. 



D. O. W. 



Within the Atom : A Popular View of Electrons and Quanta. By John 

 Mills, Fellow, American Physical Society. [Pp. xiii + 215.] (London : 

 George Routledge & Sons, Ltd. 6s. net.) 



It is often difficult for one conversant with scientific terms and ideas to assess 

 the value of a book which is written for the general reader. In this case the 

 difficulty is not so great as usual, partly because the author makes exception- 

 ally extravagant claims in the preface. The reader, we are told, need have no 

 previous knowledge of electricity, mechanics or chemistry, yet on page 4 

 reference is made to " the familiar facts of electricity." Such a reader, we 

 have no hesitation in saying, would be completely at sea with many of the 



