278 Proceedings of the Royal Society of Edinburgh. [Sess. 
The values of the rotation-dispersion were obtained by taking the 
differences of the “ Es ” and the “ Xs ” in the above table : the “ Xs ” given in 
the table below are the means of the former “ Xs ” for an obvious mathemati- 
cal reason. 
A 
aE/aa 
(0) c. 
<i) c- 
p 
(i) c. 
(!)'■• 
(l)c. 
632 
0*0785 
0*237 
0*422 
0*520 
1*22 
1*16 
574*5 
0*121 
0*383 
0*617 
0*871 
1*84 
1*94 
533 
0*141 
0*487 
0*859 
1*16 
2*54 
2*62 
501 
0*191 
0*600 
1*15 
1*61 
3 61 
3*71 
Fig . 4. 
