Notices respecting New Books. 441 



partly by reason of its novelty, has not found its way into ordinary 

 text-books. The form of instrument described is that of Crompton, 

 apparently because Mr. Fisher is more familiar with it tban with 

 any other ; the descriptions given are, however, such as will euable 

 an electrician to perform measurements with other types of instru- 

 ment. The second part of the volume deals with earlier forms of 

 potentiometer and leads naturally to the discussion of Wheatstone's 

 Bridge and its modifications. The final chapter treats of Lorentz's 

 method of determining the unit of resistance, undoubtedly the 

 most important investigation in which the potentiometer method 

 has been employed. J. L. H. 



Eine Kritilc der Nernstf schen thermodynamischen Anschauungen. 

 By Dr. Aleeed H. Bucheeee. Freiberg, Saxony: Craz und 

 Gerlach, 1897. 



This is a small brochure of thirty pages, in which the author 

 replies to criticisms by Nernst of his work on the thermodynamic 

 theory of electrochemical forces. In addition, he criticizes Nernst's 

 application of thermodynamics to the theory of migration of ions. 



J. L. H. 



Elektrische Strdrne. By Emil Cohn, Extraordinary Professor of 

 Physics in the University of Strassburg. Leipsic: S. Hirzel, 1897. 

 This volume contains the substance of ten lectures delivered in 

 Strassburg, and attended by engineers, architects, and business 

 men. The lectures aimed at giving a popular, though strictly 

 scientific, account of the generation, distribution, and measurement 

 of the electric current supplied from a central station ; they treated 

 of the magnetic, chemical, and heating effects of a current, inclu- 

 ding induction and alternating currents. The last lecture consists 

 of a short account of polyphase motors and generators. Much 

 compression is of course necessary in dealing with such a compre- 

 hensive subject within 180 small pages, but the author, by giving 

 great prominence to experiments illustrating principles and by 

 suppressing all unnecessary detail, has compiled a very readable 

 book which may prove serviceable to readers possessing technical, 

 even though not electrical, knowledge. J. L. H. 



Physilealisches Prakt'ikum mit besonderer Beruclcsichtigung auf phy- 

 sikaliscli-chemische Methoden. By E. Wiedemann and H. Ebeet. 

 Third and enlai'ged edition. Brunswick : Vieweg, 1897. 

 On the appearance of the second edition of this work, four years 

 ago, we had occasion to call attention to it as a suitable text-book 

 for first-year laboratory work. The authors have now greatly 

 extended the section on electricity and magnetism, which was pre- 

 viously the weakest part of the book. Some new experiments on 

 capillarity, notably Quincke's determination of surface-tension by 

 measuring the sizes of bubbles and globules, and a few notes on 

 manipulation, have also been inserted, thus adding to the com- 

 pleteness and usefulness of the volume. J. L. H. 



Phil. Mag. S. 5. Vol. 44. No. 270. Nov. 1897. 2 K 



