A. W. Ewell — Rotatory Polarization. 



383 



transparent jelly that practically all the moment applied was 

 applied to the former. 



July 22. Jelly tube 44. 



Moment applied 366 —366 



Twist 47 —49 



Identically same tube empty. 



Moment ..._ 366 —366 



Twist , 59 —55 



Same tube filled with water. 



Moment 366 —366 



Twist 59 -57 



^'A 



Moment (g. cm.). 



The unavoidable uncertainty in such measurements is so 

 large a fraction of the difference that no extended observations 

 were made. 



Rigidity of Rubber Tubing. — Since the rubber envelope 

 plays so important a part, the relation between couple and twist 

 was investigated for a rubber tube similar to those filled with 

 jelly, but filled with water that the interior might exert a simi- 

 lar resistance to compression as jelly without offering any 

 rigidity. 

 April 9, '01. 



Moment . 



+ Twist . 



—Twist . 



1245 1488 

 104 

 103 128 



4 cm of water. 

 325 555 784 1015 



20 40 59 80 



24 43 59 81 



These readings are plotted in fig. 7, III. The rubber tube 

 closely follows HooFs law within this wide range. 



Does the rigidity have any of the peculiarities of the rotatory 

 polarization ? 



Am. Jour. Sci.— Fourth Series, Vol. XY, No. 89.— May, 1903. 

 26 



