46 



SCIENCE 



[N. S. Vol. XLV. No. 1150 



tirely concerned witli the developments of the 

 past twenty-five years and the other articles 

 are largely taken up with such development. 

 Obviously physics is a new subject and Kultur 

 has grown in recent years. 



The thirty-six articles in this volume are 

 contributed by thirty-two specialists, all Ger- 

 mans with two exceptions — H. A. Lorentz and 

 P. Zeeman. The assignment of subjects to 

 writers is, with perhaps a couple of exceptions, 

 that which an A m erican physicist would make. 

 Thus H. Rubens writes on Warmestrahlimg ; 

 W. Wein on Theorie der Warmestrahlung ; 

 Dorn on Experimental Atomistik ; Einstein on 

 Theoretische Atomistik and Die Eelativitats- 

 theorie; Lorentz on Die Maxwellsche Theorie 

 and Die elektronen Theorie; P. Zeeman on 

 Magnetooptik ; Lecher on Die Entdeckungen 

 von Maxwell und Hertz ; Braun on Die Draht- 

 lose Telegraphic; Kaufmann on Die Kathoden- 

 strahlen und Die Rontgenstrahlen ; Max 

 Planck on Das Prinzip der Ideinsten Wirkung 

 und Verhaltniz der Theorie zueinander. We 

 are rather surprised to see that the article on 

 Die Positiven Strahlen is given by Gehrcke 

 and Reichenheim rather than by Starke. To 

 the latter is assigned Das Elektrische Lei- 

 tungsvermogen. A detailed and technical re- 

 view of this large work is here impossible, but 

 certain general characteristics may be noted. 



The authors treat their respective topics in 

 a general and philosophic manner. One rather 

 striking point is that, except in an occasional 

 appendix and except as they are required for 

 the condensed statement of a physical law, 

 mathematical equations do not occur. The 

 reader of this volume will not be troubled by 

 analytical difficulties. In this respect the 

 articles in this volume offer a striking con- 

 trast to those on similar topics in the Encyclo- 

 psedia Britannica. 



All of the material contained in these ar- 

 ticles can be found scattered through the 

 earlier handbooks or the recent scientific pe- 

 riodicals. The criticism may therefore be made 

 that this volume tells a physicist nothing with 

 which he is not already acquainted, while it is 

 of no value to one who is not a physicist, by 

 reason of the fact that the latter would be 

 unable to follow the condensed argmnent. 



This criticism, however, is rather forced. Many 

 physicists who have been carrying on inten- 

 sive work in limited fields will find here a very 

 acceptable summary of those portions of the 

 subject with the literature of which they have 

 not been able to keep in touch. 



As the contributors of the articles in this 

 volume are almost all Germans, it is natural 

 that the work of German physicists should 

 receive adequate, perhaps unduly favorable, 

 recognition. Thus Helmholtz is given credit 

 for originating the present electron theory 

 through the emphasis he placed upon Faraday's 

 statement concerning the absolute quantity of 

 electricity associated with the particles or 

 atoms of matter. Probably most physicists 

 have come to the conclusion that Faraday 

 stated for electrolysis in as clear language as 

 it could be stated the law of multiple propor- 

 tions of electricity and matter.'- Helmholtz 

 had no more experimental evidence than had 

 Faraday to extend this law beyond the field of 

 electrolysis. It required the work of Schuster, 

 Perrin, Kaufmann, Wilson, J. J. Thomson, to 

 complete the statement. If we are going to 

 give credit along this line to any one between 

 Faraday and these later workers, we should 

 not lose sight of the fact that in 1871 before 

 the British Association, Johnstone Stoney 

 spoke of the quantity of electricity appearing 

 in electrolysis as the natural unit and later 

 gave to it the name electron — a name which 

 has been retained. 



Ordinarily the writers of articles have not 

 overstated the importance of their own con- 

 tributions, but in the article on Wireless 

 Telegraphy by Ferdinand Braun full justice 

 is done to the author's experimental work. 



Passing from electricity to thermodynamics 

 one is surprised to see even in a minor para- 

 graph the name of Holtzmann preceding that 

 of Joule in connection with the determination 

 of the mechanical equivalent of heat. We 

 know that Holtzmann by his work on the 

 specific heat of gases made a contribution of 

 some importance and that he computed the 

 mechanical equivalent of heat — ^but his ideas 

 were hazy as to the nature of heat, for 



1 See ' ' Experimental Eesearches, ' ' Vol. I., par. 

 852. 



