1880.] Strained Material, Leyden Jars, and Voltameters. £27 



about a varying mean position, the true curve was drawn in accordance 

 with a method mathematically developed by us.* 



The reduction of this curve by the method previously explained 

 leads to the equation 



1^=72-84- 35-55 € -°-° 569 ', 



where w 1 is the deflection, and t the time from the moment of remov- 

 ing the deflecting couple, the unit of t being 20 seconds. Several of 

 the earlier observations have been omitted in the following table, as it 

 is not until after 40 seconds that the above equation represents ac- 

 curately the torsional strain. From this time, however, until the end 

 of the experiment, the equation is very accurate. 



Recovery of Glass Wire previously subjected to Torsional Strain. 

 November 16, 1876. 



Time from mo- 



ment of removing 



Observed 



w x calculated 



Difference 



deflecting couple. 



deflection w. 



from formula. 





07 



143-5 



107-0 



36-5 



1-0 



131-5 



106-4 



25-1 



1-5 



118-4 



105-4 



130 



2 



110-4 



104-5 



5-9 



3 



102-9 



102-8 



o-i 



4 



100-4 



101-1 



0-3 



5 



98-7 



99-5 



-0-8 



| 6i 



97-2 



98-1 



-0-9 



7 



96-0 



96-7 



-0-7 



8 



95-0 * % . 



95-4 ' .... 



-0-4 



9 



94-0 



94-1 



-o-i 



10 



92-9 



92-9 



o-o 



11 



91-9 



91-8 



o-i 



12 



90-8 



90-8 



o-o 



13 



89-9 



89-8 



o-i 



14 * 



88-8 



88-8- • . 



o-o 



15 



88-0 



88-0 



o-o 



16 



87-1 



87-1 



o-o 



17 



86-3 



86-3 



o-o 



18 



85-6 



85-6 



-o-i 



19 



84-9 



84-9 



o-o 



20 



84-3 



84-2 



o-i 



21 



83-6 



83-6 



o-o 



22 



82-9 



83-0 



-o-i 



23 



82-2 



82-4 



-0-2 



24 . . . . 



81-9 



81-9 



o-o 



* " Journal Soc. of Telegraph Engineers," vol. v, 1877, p. 391. 



