SUPPLEMENTS. 
I. NOTES SUPPLEMENTARY TO CHAPTER VI. 
6. Position of Intervals.—It is said in the text that in some 
exceptional cases the observations exhibit a marked clustering 
round certain values. The word exceptional should hardly have 
been used. Whenever there is some doubt as to the final digit 
in reading a scale, scope is given to the idiosyncrasies of the 
observer and the distribution of frequency over the final digits 
is rarely uniform. The most conspicuous feature is usually the 
tendency to round off to the nearest unit, thus making 0 the 
most frequent final digit, but 5s may also be emphasised if 
emphasised on the scale itself, and the excesses of 0’s and 5s 
may be drawn in the most diverse ways from the other parts of 
the scale. 
TABLE A.—Frequency-distributions of Final Digits tn Measurements by 
Four Observers, 
Frequency of Final Digit per 1000. 
Final Digit. 
a 2, 0. 
0 158 122 231 358 
: 97 98 37 49 
125 98 | 80 90 
73 90 72 63 
76 100 55 37 
71 112 222 211 
90 98 | 71 62 
56 99 75 70 
126 101 72 44 
129 81 65 16 
Total : J 0 
Actual ob- ) 
servations 
A. B ¢ 1; 
1001 999 100t 100+ 
1258 3000 1000 1000 
262