the Magnetic Efect of Electric Convection. 44H 



destined to detect tlie magnetic effect attributed to its 

 entniinement. 



3. That daring its entmlnement the charge undergoes no 

 variation ; in particular, that the loss by leakage is limited 

 to a very small fraction of the total charge carried. 



In the hope of reconciling the contradictory results 

 obtained by the various experimenters on this question of 

 fundamental importance, M. H. Poincare took the initiative 

 in the fall ol: 1902 to bring about a collaboration between 

 two o£ the experimenters whose results have invariably been 

 in contradiction one to the other. In accordance with the 

 suggestion of Lord Kelvin, Paris was chosen as the most 

 favourable place for these joint experiments ; and M. E. 

 Bouty gladly put at the disposal of the two investigators his 

 laboratory at the Sorbonne. 



Accordingly, invited by Messrs. Poincare and Bouty, 

 in the name of the University of Paris, Mr. H. Pender, 

 whose experiments have invariably given positive results, 

 went to Paris in January 1903 to work in collaboration 

 with M. y. Cremieu, w^hose experiments have always been 

 of a negative character. The Johns Hopkins University 

 put at the disposal of Pender all the apparatus necessary, 

 and obtained from the Carnegie Institution the funds 

 necessary to defray the expenses of the journey. The 

 expenses of the actual experimenting were met by the 

 Institute of France. 



We W'ish here to express to M. H. Poincare and M. E. 

 Bouty our gratitude for their initiative and liberality. 

 Through their invaluable aid in advice and criticism, we 

 have been able to realize in three months an almost complete 

 programme of very delicate experiments. Thanks to the 

 most excellent organization of the laboratory of M. Bouty, 

 w'e have not once been delayed by lack of apparatus or of 

 any physical means whatever. 



Also it gives us great pleasure to express our gratitude 

 for the liberalities of the Carnegie Institution, of the Johns 

 Hopkins University, and of the Institute of France. 



liepeiition of Fender^s Experiment. — Cremieu, in 1899- 

 1900 *, was led to repeat Rowland's experiment ; and, for 

 considerations elsewhere developed, he modified considerably 

 the method. Instead of the direct magnetic effect, he 

 studied the electromagnetic induction of a moving charged 

 body. The experiment gave negative results, w^hich per- 

 sisted during a long series of observations, in spite of 



._ * Cremieu, These de Paris, Gauthier-Villars, 1901. 



