716 



SCIENCE 



[N. S. Vol. XL. No. 1037 



Dr. Savage has prepared this volume of 170 

 pages as " a practical manual " dealing with 

 the bacteriology of water, milk and other food 

 products and air. It begins with two intro- 

 ductory chapters dealing in particular with 

 the significance of colon bacilli, streptococci 

 and anaerobic spore formers as " indicator or- 

 ganisms." Then foUow chapters on Water, 

 Soil and Sewage, Shellfish, Milk, Modified 

 Milk and Milk Products, Bacteriology of 

 Meat and Meat Products, Air and the Deter- 

 mination of Antiseptic and Germicidal Power. 



A book of this size covering so wide a field 

 can not from the nature of the case give a 

 complete and authoritative treatment of the 

 various subjects under discussion — such a 

 treatment for example, as Dr. Savage has given 

 to the problems of water bacteriology in his 

 excellent " Bacteriological Examination of 

 Water." On the other hand the discussion 

 seems somewhat too discursive and the pro- 

 cedures and standards of interpretation are 

 stated with insufficient clearness and definite- 

 ness to make the book altogether satisfactory 

 as a student's text-book or a practical manual 

 for the laboratory worker. Dr. Savage does, 

 however, give an excellent summary of recent 

 English discussions in regard to the subjects 

 treated, with a good list of reference to orig- 

 inal sources which will make the book valu- 

 able for advanced students. 



Erom an American standpoint the most 

 serious defect in this work is the almost com- 

 plete lack of acquaintance with the progress 

 which has been made along these lines on this 

 side of the water. It seems strange, indeed, 

 to find a book on the bacteriology of milk, 

 water, air and food with no reference to Amer- 

 ican investigations on the direct microscopic 

 examination of milk, on the lactose bile pre- 

 sumptive test, on the bacteriology of sewer air 

 and on the bacteriological examination of 



s^ellfisl'- C.-E. A. WiNSLOw 



The American Museum of 

 Natural History 



Molecular Physics. ^ By James Arnold 

 Crowther. Philadelphia, P. Blakiston's Son 

 & Co. 



This little book of 175 pages, though entitled 

 " Molecular Physics," contains in reality only 

 such material as is usually found classified 

 under the general head " Electronics." It rep- 

 resents an attempt to present in elementary, 

 almost in popular, form the recent develop- 

 ments in physics which center around X-rays, 

 the electrical phenomena observable in ex- 

 hausted tubes and radioactivity. The author 

 is himself Fellow of St. John's College and 

 demonstrator in physics at the Cavendish Lab- 

 oratory. The points of view taken are then 

 those which have grown up in that inspiring 

 atmosphere out of which have unquestionably 

 come more of the influences which have molded 

 modern physics than from any other two 

 places in the world combined. Freshness and 

 originality of treatment are to be expected 

 from such an author, and the expecta- 

 tion is not disappointed. The first two chap- 

 ters deal with the determination of e/m and e, 

 the third and fourth with the work on posi- 

 tive rays, J. J. Thomson's beautiful photo- 

 graphs being given especial attention. The 

 fifth chapter gives the usual deductions found 

 in a chapter on the nature and size of an 

 electron. The sixth and seventh chapters are 

 entitled the Chemistry of the Model Atom and 

 the Atom in Vibration and represent the best 

 elementary treatment I have seen of atomic 

 models in relation to spectroscopy. 



The eighth chapter presents just a touch of 

 the conventional molecular physics in the dis- 

 cussion of Van der Waal's equation, but the 

 last half of the chapter returns to the electron 

 theory of metallic conduction. This subject 

 is treated in the usual way, but unfortunately, 

 I think, without any attempt to explain, or 

 even to state the serious difficulties which the 

 theory encounters. This is the one place in 

 the book where the untrained reader will per- 

 haps obtain a somewhat erroneous impression. 

 The last chapter on the Atom in Dissolution is 

 a very brief survey of the subject of radio- 

 activity. Altogether the book is admirable 

 and contains elements of interest for both the 

 physicist and the general reader. 



E. A. MiLLIKAN 



