Adams — Electromagnetic Effects, etc. 155 



Art. XV I. — The Electromagnetic Effects of Moving Charged 

 Spheres ; by Edwin P. Adams. 



The magnetic effects due to moving charges were first 

 shown experimentally by Professor Rowland* in 1876. Dr. 

 E. Lecher, f in 1881, thinking that the importance of the 

 experiment rendered its repetition desirable, did so, but with 

 negative results. Insufficient data regarding his experiment 

 make it difficult to point out the cause of his failure to obtain 

 the effect. Since then, Professor Rowland's results have been 

 fully confirmed by Professor W. C. RontgenJ in 1885 ; by 

 Rowland and Hutchinsong in 1889 ; and by Professor F. Him- 

 stedtf later in the same year. 



The next experimental attack upon this problem was by 

 M. V. Cremieui" at Paris in 1900-1. His experiments were 

 originally undertaken to determine whether a changing mag- 

 netic field exerts a mechanical force upon an electrically 

 charged body. The negative results obtained led him to 

 undertake a series of experiments on the magnetic effect of 

 moving electric charges. The results of these experiments 

 are apparently all opposed to the results obtained by the above 

 observers. The data which have thus far appeared do not 

 give sufficient details to render it certain that positive results 

 should have been expected. Cremieu himself states that he 

 is convinced that the effect does not exist. 



The great importance of the experiment would seem to 

 render further investigation desirable, and the present paper 

 contains a description of an experiment with this end in view. 



All previous experiments have been made with rotating 

 disks. With one exception the direct effect of a charged 

 rotating disk upon a magnetic needle has been examined. 

 The exception referred to is the method employed by Cremieu 

 in one of his experiments where he sought to observe the 

 inductive effect of charging and discharging a rotating disk 

 upon a neighboring coil of wire in circuit with a sensitive 

 galvanometer. 



The use of charged spheres was suggested by Professor J. J. 

 Thomson** in 1881, and he gives a calculation of the mag- 



* This Journal (3), xv, p. 30, 1878. 

 f Rep. d. Phys., xx, p. 151, 1884 

 t Sitz. d Berlin Akad., p. 198, 1885. 

 § Phil. Mag. (3), xxvii, p. 445, 1889. 

 I Wif-d. Ann, xxxviii, p. 560, 1889. 



*![ Comptes Rendus, cxxx, p. 1544; cxxxi, p. 578; cxxxi, p. 797 ; cxxxii, p. 

 327. 



** Phil. Mag., xi, p. 236, 1881. 



A.M. Jour. Sci.— Fourth Series, Vol. XII, No. 68.— August, 1901. 

 11 



