Intelligence and Miscellaneous Articles. 



493 



Lines of 

 spectrum. 



X. 



Observed angles 

 of rotation. 



Total 

 num- 

 ber of 

 obser- 

 vations. 



Mean. 



Calcu- 

 lated. 



Differ- 

 ence. 



A 



7600 



718-5 

 686-7 

 656-2 

 588-9 

 526-9 

 486-07 



430-72 



410-1 



396-8 



381-9 

 372-7 

 3720 



358-5 



12-62 

 12-76 

 15-69 



2*i*82 



27-68 

 32-98 

 32-86 

 42-67 

 47-52 

 5b21 

 51-12 



64-76 



12-68 

 14-35 

 15-82 

 17-35 

 21-78 

 27-57 



47-52 

 51-23 

 51-16 

 51-33 

 51-10 

 56-05 

 55-71 



59-18 

 59-20 



64-73 



o 



14-33 



32-76 

 32-82 

 42-59 



5i-37 

 51-37 



59-03 

 59-31 



64-28 



20 

 16 

 12 

 6 

 10 

 10 

 18 



12 

 14 

 46 



12 



8 



21 



28 



12-68 

 14-33 

 15-75 

 17-35 

 21-79 

 27-61 

 32-85 



42-63 

 47-52 

 51-22 



55-88 

 59-03 

 59-24 



64-41 



12-78 

 14-33 

 15-75 

 17-35 

 21-74 

 27-55 

 32-78 



42-69 

 47-47 

 51-22 



55-80 

 58-99 

 59-24 



64-44 



+010 



o-oo 



000 



o-oo 



-005 

 -0-06 

 -0-07 



4-0-06 



-0-05 



0-00 



-0-08 

 -004 

 -000 



+0-03 



a 



B 



C 



D 



E 



F 



G- 



h 



H, 



L , 



M 



3rd strong 1 

 line of the I 

 group M J 



N 





The third, fourth, and fifth columns give, in degrees and decimal 

 fractions of a degree, the values of the angle of rotation as obtained 

 in the three different series of observations, referred to a plate of 

 quartz 1 millim. thick. The second series of experiments was made 

 with two prisms to the spectroscope from A to E, with only one 

 for the more refrangible lines ; series I. and III. were made with 

 but one prism. The numbers given are most frequently the mean 

 of six observations, but sometimes of four, eight, twelve, or sixteen. 

 The values given in the eighth column were calculated by Boltz- 

 mann's formula, as we shall subsequently see. 



The accordance of the different series varies a little, according to 

 the lines, which are not all of equally easy adjustment. For the 

 line Hj, for example, there is some divergence, because the nearness 

 of the line H 2 somewhat impedes the observation ; and it is the 

 same with the numerous lines of the group L. The lines M are 

 very distinct ; but the feeble luminous intensity of N considerably 

 lessens the precision. 



The results recorded in the seventh column approach very nearly 

 those obtained by MM. Broch and Stefan, viz. 



Broch 

 Stefan 



P. 



15-30 



o 



17-24 

 .15-55 17-22 



D. 



21-67 

 21-67 



E. 



27-46 



32-50 



G. 



42-20 



H. 



27-46 32-69 42-37 50-98 



