Trowhridge and Penrose — The Thomson Efect. 3b 



If the deflections in II and III are subtracted from the co 

 sponding deflections in I, we get the amount of deflectio 

 ie to the Thomson Effect. It will be observed that all tt 

 •flections in II are less than those in I, and those in III ai 

 eater, as they obviously should be. The only inaccuracy i 



2-65 315 0-25 0'25 



ii.U.1,.. 



alt.<rati< 



the fact that we neglected the 

 i of the nickel due to the slight 

 change in temperature. 



The numbers in these tables are obviously too small to draw 

 any conclusions. They, however, confirm the preceding results 

 M to the direction of the Thomson Effect, and tend rather to 

 i to disprove the reversibility of the effect. The ex- 

 periment was repeated several times, but with no better result. 

 . Experiments were also made to test the influence of magnet- 

 ism on the Thomson Effect. Nothing but negative results 

 were, however, obtained. 



The strip of nickel was placed horizontally, with its flat sur- 

 face perpendicular to the axis of a large electro-magnet— the 

 I . tween the two poles of the magnet. One surface 

 " [ the nickel was pressed against one pole; on the other sur- 

 face was placed one face of the thermopile, while the opposite 

 •ace was in contact with the second pole of the magnet. Mica 

 was used, as in the previous experiments, to protect the faces 

 ot the pile. The whole was wedged, and pressed tightly to- 

 I clamped by means of wire, the object being to pre- 

 vent any motion of the nickel when the magnet was made. 

 One end of the nickel was heated by a Bunsen burner, the 

 other was at the temperature of the ai'r. Six hours were re- 

 quired for the apparatus to reach a condition of thermal equi- 

 ''"'iiuii. The electro-magnet was connected with thirtv-eight 

 freshly set-up bichromate of potash cells, with plates of large 

 «ze. A current from eight Grove cells was now passed along 

 tl 'e nickel, with and without the circuit of the magnet being 

 n^de. The deflections of the galvanometer were exactly the 

 same in each case, showing that in a magnetic field— at least 

 of the strength in the experiment— the Thomson Effect was 



unaltered. 



nfortunate that the strength of the field could not be 



