16 



Mr. S. Bidwell. 



[Feb. 1, 



Table XIV. — Effect of Pressure upon Resistance of Bismuth Contacts 

 with Constant Currents. 



Pressure 

 Grrms. 



Eesistance of contacts -with current of 



"1 ampere. 



*01 ampere. 



'001 ampere. 



•05 



5 



20-82 



182 



•1 



2 



16 -92 



143 3 



•15 



2 5 



14 60 



97 -8 



•2 



3 9 



12 60 



46 



•25 



2-6 



10 -05 



41 6 



•3 



2 -4 



6 35 



16 9 



'35 



2 -1 



4 -12 



21 -6 



•4 



1 *9 



2 37 



30 -6 



•45 



1 5 



160 



18-3 



•5 



1-45 



1-47 



3-8 



1 



•95 



135 





1-5 



•85 



•70 





2 



•90 



•62 





2 5 



•70 



•30 





3 



•50 



•15 





3-5 



•55 



•07 





4 



•35 



•05 





4-5 



•25 







5 



15 







15. Permanent Red uction of Resistance due to Pressure. 

 Repeating with bismuth the experiments already described in the 

 case of carbon, it was clear that the diminution of resistance effected 

 by pressure is generally of a permanent nature, continuing to a 

 great extent after the pressure has been removed (so long as the 

 points of contact remain undisturbed), and thus reversing the case 

 of carbon. With strong currents the variations of resistance were 

 so uncertain and irregular that accurate measurements were impossible ; 

 but with a resistance of 300 ohms between the battery and the bridge 

 the effect is very clearly marked. The results of the experiments 

 thus made are tabulated below. 



Table XV. 







Resistance of bismuth contacts. 





Pressure. 















Grrms. 

















Ohms. 



Ohms. 



Ohms. 



Ohms. 



Ohms. 



Ohms. 



•5 



10 '9 



37-5 



16 3 



14 5 



25 5 



62 



3 



1 3 



1-7 



•5 



1 



11 



1-8 



'5 



1-5 



1'7 



•5 



4-5 



5 5 



15 



