19 



stress that the ZA molecules exercise upon the Iron rnolc- 



-.ho'Ain.; th.it the fir -.t contact of heat is by far the 



> curves represent hich 



the I els along the bars of ZA and Iron. But, of 



course, the rate varies according to and 



according to the iron used, whether hard. annealed 



*9. 



2. A 



In these striking facts we think we have light cast upon 

 ^iul shall find that we have something to work 

 upon. We learn that ZA, haviru it >m< than Iron, 



t!u- iirarrst j>ortionof the- ZA bar is heated before a similar 

 portion in the Iron bar, although the Iron is almost four 

 times a better conductor of heat So that it i- not the 

 molecules of the Iron swinging in ft I with vibra- 



tory stress against the ZA that causes the flow of 

 electricity, but it is the molecules of the ZA Dinging 

 in fi r with vibratory stress against the mole- 



.>t~ the In-n This can further be explained. In this 



