Producible by Attrition and Contact of Metals. 



19 



4. When the rheophores and metals are transposed in the binding screws, 

 attrition at equal temperatures will cause east deflection. 



5. If the second-named metal, now on the zinc side, be cold, and the first 

 named hot, the deflection will be east. 



6. If the second-named metal, now on the zinc side, be hot, and the first 

 cold, the deflection will be we st. 



It thus appears that, in conformity with the paradigm, the conditions 2 and 6 

 are those under which the simulated reversals would take place ; but in 2, the 

 first-named metal, being on the zinc side, ,must be the cold one ; and in 6, the 

 second-named metal, being on the zinc side, must be hot, and its associate cold: 

 hence the conditions 2 and 6 are reversed with regard to temperature. 



In short, a true reversal could not take place unless attrition and thermo- 

 contact were capable of producing opposite efiects under the same circum- 

 stances of temperature and arrangement of the metals. No instance of this 

 kind occurred during numerous experiments. Indeed, it would be surprising 

 if opposite effects could result from processes so similar in their nature as con- 

 tact and attrition, under circumstances exactly the same. 



There are many associations in which it would be impossible that attrition 

 should even simulate a reversal of the effects of contact, no matter in what re- 

 lation the metals are placed with regard to each other, or their temperature. 

 Thus a third class of metallic associations exists which differs entirely from the 

 former two. A number of these shall be adduced, not only as examples, but 

 with an ulterior view which will appear hereafter. 



Lead with iron. 

 Zinc with iron. 

 Silver with iron. 

 Platinum with iron. 

 Palladium with iron. 

 German silver with iron. 

 German silver with nickel. 

 German silver with silver. 



German silver with zinc. 

 German silver with brass. 

 German silver with copper. 

 German silver with lead. 

 German silver with cadmium. 

 Antimony and iron. 

 Nickel with arsenic. 

 Nickel with antimony. 



The last-mentioned pair of metals is an excellent example of this class, its 

 deflections, whether at equal or unequal temperatures, being well marked. 



d2 



