344 Yon Tunzelmann on the Production of Thermoelectric 



42 lbs., the deflection changed rapidly to 14 U.S., and in about 

 an hour fell to 8 U.S., and in 40 hours to 3 U.S. 



Experiment 5. — A steel wire *6 millim. diameter. = 13°. 

 Initial deflection = about 1 U.S. W = 63 lbs. Direction of 

 current after application of weight U.S. The weight was now 

 left suspended for about 40 hours; but the apparatus received 

 an accidental jar before the permanent deflection could be ascer- 

 tained. The weight was then removed, causing a deflection 

 of 8 S.U., gradually increasing to 11, and then decreasing 

 much more slowly than it had increased. 



Time from removal ^ 



of strain (minutes). 



3 3-5 



6 4-5 



9 3-5 



12 2*5 



15 1-5 



18 -87 



36 ..... * 



The effect of rapidly putting on and taking off the weight 

 a number of times in succession was then tried; and it was 

 found that each time the weight was put on the deflection 

 diminished, while each time that it was taken off the deflection 

 was increased up to a certain limit. The immediate increase pro- 

 duced by taking off the weight was greater than the immediate 

 decrease produced by putting it on ; so that on the whole there 

 was a large increase in the current, the deflection being got 

 up in this way to nearly 30 S.U., falling again very rapidly 

 if the weight were left attached to the wire. Under these cir- 

 cumstances the deflection went down rapidly to zero, changed 

 sign, rose to a maximum, and then again began to diminish, 

 passed through zero in the opposite direction, and so continued 

 to perform excursions in alternate directions, and very rapidly 

 decreasing in extent. When the weight was permanently 

 removed the deflection of the galvanometer died out much 

 more slowly, and the changes of sign were only just percep- 

 tible. These phenomena confirm the conclusion to which I 

 was led by the former experiments, that there is, besides the 

 main effect, a transient effect produced by altering the strain 

 on the wire ; and this transient effect appears to me to be due 

 to the molecular state of the wire making a partial return after 

 the first shock towards its primary condition, just as the im- 

 mediate deflection of a spring suddenly stretched by a weight 

 is greater than when it has come to rest in its position of equi- 

 librium. The changes of sign in the current as it gradually 



