26 



I made- another experiment upon one of the same kind 

 of couple-, trying \\hat cftcct could be obtaiiu-d by putting 

 it into a powerful :efully insulating tin- jaws, 



connecting the leads up from the couple to tin galvanoi 

 and putting considerable pressure upon the handle of the 

 vice, I found about 2 indicated. Left thus for about ten 

 days the same current was shown ; left again, but this time 

 for three months, all the current had gone. Hut on 

 unscrewing the handle of the vice, the galvanometer 

 indicated a small current. 



I have thought it better, as mentioned at the outset, to 

 confine our attention to these two metals in conjui 

 with each other. In dealing with other metals or alloys, 

 their physical properties and characters have to be carefully 

 examined and thoroughly enquired into, to understand, in 

 a small measure, what work their atoms and molecule 

 doing. 



It is most interesting to turn up the experiment 

 Krman, who showed that a violent blow struck by one 

 substance upon another, produces opposite electrical 

 on the two surfaces, and found that taking the thermo- 

 electric scries of metals, each substance will take a + 

 charge on being struck with one lower on the list. Bismuth, 

 German Silver, Lead, Platinum, /inc, Copper, Iron, Antimony, 

 etc., etc. This again goes to prove the theory with which 

 irted, since the violent blow given, places the molecules 

 of each of the two metals, each substance having physical 

 rtics of its own, in a state of stress, so that if these 

 blows could be continuously delivered, cog wheel friction 

 would be set up, and an E. M. F. produced. Since this 

 this state of molecular tension this static electricity 

 remaining always runs to the weakest part of any particular 

 body, it 'naturally remains upon any point of a large body 

 where the molecules are most at liberty to come into play, 

 rather than in the mass of the body itself; and perhaps the 



