C. Bancs — Counter -twisted Curl Aneroid. 



125 



the amount of counter-twisting, and apparently reaches a limit 

 at about 150°. From here on, however, the evidences of per- 

 manent set were met with. They are in the direction of the 

 uncoiling, showing the spring to have acted on the curl. At 

 the end of the experiment, when the spring was released, about 

 90° of permanent set had been imparted to the curl. I believe 

 therefore, that the curl could have been made even more sen- 



Chart showing the inverse sensitiveness (ordinate) of 

 a counter-twisted system varying with the amount 

 of counter-twist (abscissa). 



sitive than shown in figure 3, if its material had been resilient 

 and of high viscosity. At all events, the datum reached (50 cm 

 Hg corresponding to a degree of deflection between the ends 

 of a linear cm. of the turns of the curl) is markedly in excess 

 of the results given at the end of § 7, while the apparent vis- 

 cosity of the metal has now no serious significance. Indeed 

 since the viscous set above was actually negative (uncoiled curl), 

 whereas in the simple curl (§ 5 et seq.) it is positive, a virtual 

 elimination of viscosity is clearly possible. 



Table 2. — Showing the increased sensitiveness resulting from 

 increased coun ter-twisting. 



Turns of 



vn 6 



Counter-twist 



in degrees 



of arc. 



Pressure 

 per degree, 

 per turn. 



Pressure per 

 degree, per 

 linear cm. 



Kemarks. 



No. 



o 



cm., Hg. 



cm., Hg. 





2-5 

 2'3 





 60 



13-6 



99 



120 

 95 



No viscosity. 



2-1 



100 



6'6 



69 



a ct 



1-9 



140 



4-3 



50 



u u 



VI 



180 



4-3 



56 



{ Curl shows negative 

 ( viscosity. 



2-3 (released) 



10-0 



98 



j Curl shows 90° set 

 { after releasing spring. 



