L 149 ] 



XXIII. Notices respecting New Boohs. 



Die elektrodynamischen Grundgesetze und das eigentliche Elementar- 

 geselz. By Eranz Kerntler. Buda-Pesth: Lloyd-Gresellschaft, 

 1897. 

 rPHIS work is a pamphlet of nearly 70 pages, devoted to the 

 ■*- discussion of expressions for the values of the forces exerted by 

 an element of current on a second element situated at a distance 

 from it. While investigating experimentally the laws of the 

 mutual action of closed circuits, Ampere was led to assume that 

 the mutual action of two current elements is a single force acting 

 along the line joining them. This assumption has been greatly 

 criticised ; according to it no force is exerted between two elements 

 at right angles to each other in the same plane, and the possi- 

 bility of the mutual action giving rise to couples is not considered. 

 Stefan generalized the theory by including forces between elements 

 at right angles, and Korteweg introduced the consideration of 

 couples, but in each case the expressions contain more constants 

 than can be determined by experiment. 



The author poses as a strong advocate for Stefan's theory, and 

 points out that, in Stefan's equations, two of the constants which 

 have hitherto been supposed different are necessarily equal ; this, 

 however, still leaves the constants indeterminate. JNo mention is 

 made of Korteweg's work, nor does the author anywhere contem- 

 plate the possibility of couples. He is apparently aggrieved that 

 the work of Stefan has received slight recognition, except in 

 Germany, and especially because Maxwell makes no reference to it 

 in his treatise. Such negligence is perhaps sufficiently atoned for, 

 as far as England is concerned, by the exhaustive Keport on 

 Electrical Theories which Professor J. J. Thomson communi- 

 cated to the British Association in 1885. Since that time the 

 aether theory of electricity has received so much experimental 

 confirmation that all others possess little more than historical 

 interest. J. L. H. 



Practical Electricity. A Laboratory and Lecture Course for First 

 Year Students of Electrical Engineering. Vol. I. By W. E. 

 Atkton, F.R.S., Assoc. M. Inst. C.E. London : Cassell & Co., 

 1896. 



In some respects Professor Ayrton's new work may be described 

 as the second edition of a volume with the same title which he 

 wrote ten years ago. A comparison of the two books will, however, 

 immediately reveal the great amount of alteration and enlargement 

 which has been rendered necessary by a decade of advance in 

 electrical technology. The standard instruments of those days 

 are now classified as early forms, electric power and energy are 

 ranked in importance along with current, potential, and resistance, 

 Phil. Mag. S. 5. Vol. 43. No. 261. Feb. 1897. N 



