6 M. Gr. Wiedemann on Torsion. 



increasing weights + W, when" the following numbers were 

 obtained : — 



w= 



. 44 



64 



84 



104 



124 



T 



1857 



2077 



2295-8 



2524-8 



2753 



P 



1408-5 



1425-5 



1443 



1464 



1486-2 



T-P 



448 ; 5 



651-5 



852-8 



10608 



1267 



A 



203 201-3 208 206 2 



Here, as in the previous experiments, after repeated twist- 

 ings and untwistings the temporary and the permanent final 

 states of the wire were much more quickly reached than at the 

 first action of the twisting forces. 



5. Torsion of a partly untwisted Wire. — Another, similar 

 wire was again and again twisted to and fro by the weights 

 ±120, till its torsions were no longer altered on the renewed 

 application of the same forces. Again the limits within which 

 the temporary and the permanent torsions were confined con- 

 tinually approached one another. Thus, at the first and the 

 sixth torsion they amounted to : — 



I. 



VI. 



W - 120 



4- 120 



- 120 



+ 120 



T -1343 



+1415 



-1328 



+ 1401 



T, -1366 



+1431 



-1334 



+1406 



P — 75 



+ 145 



- 52 



+ 119 



P x — 72 



+ 143 



- 50 



+ 118 



T+120-T-120 2758 



2797 



2729 



2740 



P +120 -P_i 20 220 



215 



171-5 



168 



The wire was next twisted once more by increasing weights, 



when the permanent torsion remained +118; the temporary 



torsions amounted to : — 



W= +30 + 40 + 50 + 60 + 70 + 80 + 90 + 100 + 110 + 120 

 T = 430 535 642 749 857 964 1072 1180 1288 1396 

 T-P 312 417 524 631 739 846 954 1062 1170 1278 

 A 105 107 107 108 107 108 108 108 108 



After this the permanent torsion (118) of the wire was re- 

 duced to lower values by the weights.'— 20 to —120, and the 

 wire each time again twisted by increasing weights in the 

 positive direction. The operation was afterwards reversed. 

 The results are contained in the following Table, in which T 

 and P denote the temporary and permanent torsions obtained 

 at the reductions. 



The results of the first observations (reduction by negatively 

 acting weights) are more exact, because the finally valid 

 action of the weights was longer waited for. They are on 

 that account delineated in the curves in Plate I. fig. 2, of 

 which the ordinates give the permanent torsions P — P , and 

 the abscissae the twisting weights. Moreover it follows im- 

 mediately from the numbers of both Tables that, reckoning 

 from the torsion P which remained at the reduction, the tern- 



