376 A. W. Ewell — Rotatory Polarization. 



Theoretically the relaxation should make the odd rotations, 

 — 19, —25, etc., increase, while the even, 10, 11, etc., should 

 slightly decrease. The increase of the latter is due to the other 

 effect of a previous twist, which also causes the odd rotations to 

 increase faster than they would by simple relaxation. 



Under prolonged stress the rotation increases in contrast to 

 the decrease with prolonged strain. 



July 21. Tube C 4 . Weight of — 180 g applied to cords at 10-18. 



Time 10*20 10-30 10-35 ]0'37 10'45 



Rotation 11 14 +130^ applied — 7 —13 



July 22. Tube F 1. 180^ applied at 11-13. 



Time 11-15 -20 -25 -30 -35 -50 12-08 



Rotation —25 —28 —33 —35 —38 —38 —180* applied 



Time (cont.).. 12-08 -11 -21 -37 

 Rotation " .. 34 39 52 53 



The stress being constant, the actual strain is constant but the 

 prolonged state of strain increases the rotation. 



Influence of Temperature. — As would naturally be expected, 

 the rotatory polarization decreases with rise of temperature, 

 owing to decrease of strain with increased relaxation and a 

 more fluid condition of the jelly. Throughout this work it 

 has been noticed that the softer and more fluid the jelly the 

 less the rotation. 



Aug. 6. Tube E 1. Twist of 90. 



Temperature 23° 36 37 



Rotation —31 —25 —10 



Tube E6. Twist of -90. 



Temperature .. 23° 38 38 23 Repeating 23 

 Rotation 26 15 3 4 Twist 21 



The jelly tube was loosely surrounded by an electric heating 

 coil. A thermometer between the jelly tube and the coil gave 

 the temperature. 



From the above we should expect that with a given jelly 

 tube, the lower clamp being freely suspended from it and the 

 cords which apply the twist being horizontal, the position of 

 the lower clamp for zero twist being read before and after each 

 twist, sufficient time being allowed for the jelly tube to 

 approximately reach zero twist, a uniform, short time being 

 allowed after the twist is applied before the rotation is read, 

 and a considerable time intervening between a large twist and 

 a succeeding small twist, the temperature being approximately 



