SOME PHYSICAL PROPERTIES OF ICE 



6ii 



It was found that it took about lo minutes to reach the new 

 equihbrium position when an ice bar is twisted by a certain stress 

 within the elastic limit. The deformation in the foregoing obser- 

 vation in the part AB, therefore, must be slightly modified for 

 this effect. Careful observations were made, increasing the load 

 by the same amount at intervals of 20 minutes. As the result it 

 was found that the mean deviation was 5' 2 per 26 gm. on the 



Fig. I. 



2 4 6 8 10 12 



Torsion in degrees 

 -Torsion curve of an ice bar, 13. 15 cm. long and i . 73 cm. in diameter, 



with crystals transverse to its longer dimension. Arm of the torsional couple 7 . 45 cm. 

 Temperature — 7°.oC. 



scale pan, the temperature being kept at — 7?5C. 

 and other known values of the constants, we obtain 



«=i.9Xio^ c.g.s. 



From this 



The value of n was calculated from data in several experiments 

 intended primarily for other purposes. The following table gives 

 the values of n thus obtained for ice bars with optic axes of their 

 component crystals transverse to them. 



Temp. (C.) nXio~ 



— II .7 2.0 



— II .7 2.0 



— lo.o 1.6 



— lO.0 2.1 



— 9-5 2.0 



Temp. (C.) 



-9-3-- 

 -7 

 -6 

 -6 



-4 



wXio 

 . 2.1 

 . 1.9 



. 1.6 

 . 1.6 

 . 1.6 



