106 



SCIENCE 



[N. S. YoL. XXXIX. No. 994 



" Es sind dies eben Dinge, die sicli wirklich 

 gegenwartig nieht, oime gegen da3 Postulat 

 der Objektivitat zu siindigen, mit wenigen 

 Worten abtun lassen. Ein Blick auf Casparis 

 Literaturverzeichnis, das melir als ein halbes 

 Tausend Abhandlungen umfasst, wird Ihnen 

 zeigen, dass ich darin recbt tue " (pp. 475-4T6). 



In conclusion the reviewer is tempted further 

 to quote the judgment of von Fiirth respecting 

 the duty of an investigator to correlate his own 

 experiences so that they afford a logical sum- 

 mary of his undertaking. Thus in referring 

 to the myriad of details published in recent 

 years by London and his pupils on the physiol- 

 ogy and chemistry of the digestive functions 

 von Fiirth remarks : 



" Ich bin ehrlich genug, um ofFen einzuge- 

 stehen, dass ich mich einer Wiirdigung dieser 

 ungeheuren Eiille von sicherlich sehr verdienst- 

 vollen Einzelbeobachtungen nicht gewachsen 

 fiihle. Eine solche wird wohl erst dann 

 moglich sein, wenn London selbst sich einmal 

 der Miihe unterzieht, dieselben im Zusammen- 

 hange kritisch zu verarbeiten und seine leiten- 

 den Gedanken, die auf so viele Publikationen 

 verteilt sind, dass der Aussenstehende den 

 Zusammenhang verlieren muss, hervorzuheben. 

 Es ist dann zu hoffen, dass sich aus diesen und 

 anderen Arbeiten, welche verwandten Zielen 

 zustreben allmahlich ein abgerundetes Bild des 

 Eiweissabbaues im Darme in seinen einzelnen 

 Pha§en gestalten wird" (p. Yl). 



To those who wish to orient themselves in 

 the changing aspects of physiological research, 

 particularly its chemical manifestations, the 

 lectures by von Fiirth will surely serve as a 

 stimulating guide. Books of this type are rare. 

 Lafayette B. Mendel 



Sheffield Scientepic School, 

 New Haven, Connecticut 



Alternating Currents and Alternating Current 



Machinery. By D. C. and J. P. Jackson. 



New York, The Macmillan Company, 1913. 



Pp. viii + 968, 521 text figures. Price, $5.50. 



This new edition of a well-known work fur- 

 nishes one of the best general treatments on 

 the subject of alternating currents, as did the 

 first edition in 1896. Rewritten and expanded 



to twice its former size, it forms a very com- 

 plete and, on the whole, well-balanced treatise. 

 The work is attractive, the style easy and the 

 illustrations, many of them diagrammatic, are 

 instructive. Descriptive and mathematical 

 discussions are combined throughout, and 

 examples from practise are used to illustrate 

 theory. 



Attempting to cover so much in a single 

 volume assigns a formidable task to both 

 author and reader. Although on the whole 

 satisfactory, the treatment might to advantage 

 have been made more systematic; the book 

 would not have suffered by being more con- 

 densed. The chapters on synchronous ma- 

 chines (185 pages) and on transformers (155 

 pages) approach special treatises on these sub- 

 jects. The latter would be improved by com- 

 plete rearrangement, the discussion of mutual 

 induction forming not so suitable an introduc- 

 tion to the transformer, in a book of this kind, 

 as would a discussion of diagrams and equiva- 

 lent transformer circuits that are discussed 

 later in the chapter. The discussion of power 

 and power factor is particularly satisfactory 

 and complete. 



That the authors omitted many historical 

 footnotes seems unfortunate. Such notes not 

 only serve to give credit where it may be due, 

 but they make possible for the reader a more 

 detailed study of special subjects than the 

 limited description of any one text will permit. 

 The footnotes retained (and these are not a 

 few) prove their value. The authors refer in 

 their preface to the intentional omission of 

 many notes on the ground that they are un- 

 essential for undergraduates. But the scoi)e 

 of the book justifies no such limitation; its 

 field is much wider than the undergraduate 

 class-room. The book should find many 

 readers whose undergraduate days have long 

 since passed. The authors are to be thanked 

 for its production. 



Frederick Bedell 



coenell tjniversitt 



Petrogr aphis ches VademeTcum. Second edi- 

 tion. By E. WEmscHENK. Freiburg ird 

 Breisgau and Saint Louis, Mo., Herder Pub- 



