Strains Mechanically Applied. 169 



per unit of length of system, per unit of r. It must be 

 borne in mind that (0 — 0')/t is a fmiction of t, for which 

 reason the same rate of twist is applied to the wires throngh- 

 oiit ; applied, moreover, positively and negatively for each 

 value of &. Finally, after testing the wire in the drawn 

 state, it was softened by heating to redness in air and again 

 tested. In this case viscous motion at the mirror nearlv 

 ceases, thus affording an excellent check t)n the validity of 

 the experiments. 



Table IV. — Viscosity of Hard-drawn Steel Wire compared 

 with Soft. 2p = -682 centim. ; L = ; + Z' = 30 centim. + 30 

 centim. 



Wire drawn m 



oderatelj 



resilient. 



Same wire annealed at red heat in air. 



e. 



r. 



Time. 



^"^'xm 



e. 



r. 



Time. 



^-"^'xlO^ 



b: 



2i<p+<p'). 





T 



6'. 



2(0 +f). 





r 







h m 







h m 





30 



+•1041 



1 36 





30 



+ 1034 



3 08 





30 





38 



•00 



30 





10 



+-00 







39 



ro8 







11 



-10 







44 



3-33 







13 



•07 





+ 0037 



48 



4-43 







16 



•10 













+ 0014 



20 



■14 



30 



-•0989 



1 51 





30 



-1019 



3 22 





30 





53 



- -00 



30 





24 



+-00 







54 



-101 







25 



■00 







56 



-235 







27 



-03 







59 



-3-58 







30 



•07 





-•0068 



63 



-4^61 





-■0028 



34 



•07 



100 



+•0989 



2 24 





100 



+ •1047 



4 00 





30 





26 



•00 



30 





02 



■00 







27 



2-83 







03 



•33 







29 



653 







05 



•78 







32 



10-23 







08 



1-31 





+•0058 



36 



13-60 



100 



+ 0000 



12 



r44 



100 



-0931 



2 39 





-1004 



4 13 





30 





41 



•00 



30 





15 



-•00 







42 



3^03 







16 



-•33 







44 



7-07 







18 



-•88 





-•0116 



47 



10-77 





-•0043 



21 



1-65 



