94- Prof. E. Wartmann's Fifth Memoir on Induction. 



160. The tube AB was arranged in the centre of another, 

 upon which was wound four metres of a copper wire covered 

 with silk. In this wire the current of ten powerful Grove's 

 elements was excited ( 1 39.), and rendered intermittent by 

 means of the commutator described (122.). The rheometer 

 was sheltered from the electro-magnetic influence of this long 

 bobbin. The induction produced in the, mercury contained in 

 AB in no degree changed the constancy of indication of the 

 instrument. 



161. The same result was obtained by inserting into the 

 inductor cylinder the portion of the wire a which joins the 

 rheometer with the cup F. These two experiments confirm 

 the conclusions detailed in § XIII. 



162. Care was taken to alternate the direction of the cur- 

 rent of the battery P in each of the preceding experiments, by 

 placing the pieces r and s one while parallel, at another cross- 

 ways ; that is to say, by putting the cup p in communication 

 with E, then with F, and joining the cup q with F, then with 

 E. These changes in the direction of the current caused in 

 it corresponding ones in the direction of the deviation of the 

 needle of the rheometer, but did not alter the magnitude of 

 that deviation. 



163. Thus the fundamental fact is established, that electri- 

 city in the form of a current is not transmitted by rectilinear 

 radiation. Does its propagation result from section to section 

 in the bodies called conductors, as is admitted in the case of 

 caloric by contact ? This daily appears more probable, not- 

 withstanding the extreme velocity with which it is effected. 

 I propose very soon to examine the electricity of tension in 

 the same point of view. 



164<. I may observe, that the conclusions of the present in- 

 vestigation confirm those of my second memoir. It may have 

 been objected, that if electricity is propagated by undulations, 

 comparable from their extreme minuteness to those which 

 constitute light, none of the three methods which I have em- 

 ployed is sufficiently precise to testify for or against the inter- 

 ference. I shall not appeal to the probability that this latter 

 would be shown, at least once, in the hundreds of repetitions 

 which have been made of each experiment : it is sufficient for 

 me to observe, that as rectilinear propagation does not exist, 

 interference is impossible. 



