N. 



A. 



25 



320 



31 



356 



35 



387 



476 On Double-Refraction in Moving Viscous Liquids. 



by Umlauf for a number of other liquids can satisfactorily be 

 used in a calculation of such refinement. Nevertheless, here 

 is a series of experiments relating to collodion (p. 309 of the 

 paper quoted) : 



A/N. A(1+BN 2 T 2 )/N. 



10~ 4 128.10-5 152-4. 10- 5 



118 152-6 



111 152-5 

 The following is another series relating to the same 

 substance (p. 314) : 



N. A. A/N. A(1+BN 2 T 2 )/N. 



25 211. 10~ 4 844. 10- 6 108 . 10~ 5 



32 232 725 106 



35 261 746 116 



These two series were obtained with two different forms of 

 apparatus ; hence the coefficient B did not have the same 

 value in each case. The temperature of the liquid varied 

 within about two degrees, the mean being 16° C. In cal- 

 culating the figures in the last column we have taken 

 T== 0*0021 9 sec. A comparison of the two series has already 

 been made by Umlauf himself. The mean of the results 

 entered in the last column is 152*5 . 10 -5 for the first table, 

 and 110 . 10 -5 for the second ; the ratio of these two means 

 is therefore 1*387. If we calculate the ratio of the values 

 which we should have to give to the coefficient A according 

 to (1), § 7, in these two series of experiments, we find 1*561. 



The results of the experiments carried out by G. de Metz 

 lend themselves still less readily to this kind of calculation. 

 The following is the only series of experiments which we 

 have found it possible to utilize. It refers to castor-oil at 

 25° C. (de Metz, I. c. p. 504) . T has been put =0*0013 sec. 



N. 



A. 



A/N. 



A(1 + BN 2 T 2 )/N. 



6-90 



47.10- 3 



68 . 10- 4 



69 . 10~ 4 



8-10 



52 



64 



65 



8-33 



53 



64 



64 



8-57 



55 



64 



65 



8-82 



57 



65 



65 



11-77 



78 



66 



68 



12-00 



79 



65 



67 



13-04 



83 



64 



66 



13-64 



82 



60 



62 



20-00 



108 



54 



58 



20-83 



113 



54 



58 



30-77 



150 



49 



57 



35-71 



175 



49 



60 



38-46 



181 



47 



59 



41-66 



194 



47 



61 



55-55 



249 



45 



69 



