186 



BELL SYSTEM TECHNICAL JOURNAL 



1000 

 900 

 800 



700 

 600 



500 



10 



2 400 



Z 300 

 < 



200 



100 



3 4 



FORCE IN DYNES 



7 8 9 10 



Fig. 21 — Typical resistance-force characteristics of carbon granules pressed against 



a polished carbon plate. 



2 4 6 8 10 12 14 16 18 20 22 



AD IN CM X 10"^ 



Fig. 22 — Effect of the extent of contact motion (A£>j on A^and A^". (Average values.) 



