the Carbon Disk of Edison's Tadmeter. 117 



below were obtained, which, though necessarily somewhat 

 scattering, were so situated as to render its general form 

 almost certain. In almost every instance, immediately after 

 the removal of the pressure the normal resistance was again 

 measured; and it was found that while time was necessary for 

 the resistance to reach a minimum after the application of the 

 pressure, the disk seemed to recover its maximum normal 

 resistance instantly upon its removal. 



6 -30 



3-00 10 m. 20 m. 30 m. 40 m. 50 m. 60 m. 



Time. 



Curve showing the relation between Eesistance and Time. 



After the construction of the curve showing the relation 

 between time and resistance, and on the supposition that it 

 correctly represents that relation, it was easy to know what 

 the adjustment of the bridge should be at the end of any 

 given time; and thus the difficulty of that adjustment disap- 

 peared. 



When tested in this way, the curve was found to be correct 

 within the errors of experiment. The following table exhibits 

 the resistances after various times, the instantaneous resistance 

 being called 100. The resistance before the addition of the 

 pressure of 50 grams was 11*67 ohms, which immediately fell 

 to 3*52 ohms upon the application of the weight. 



