FORCE OF THE WESTON NORMAL CELL IN SEMI-ABSOLUTE VOLTS. 
157 
which were clamped on to the comparator (see § VI. (c)) at a distance approximately 
equal to the distance between the fixed coils. Comparisons of the comparator 
readings with the caliper measurements gave an accurate calibration. As it was 
found difficult to make the blocks absolutely rectangular the mean of the two 
measurements with the blocks placed on their opposite faces was taken in every 
case. The following is a summary of the calibration in which the values are reduced 
to those corresponding to a setting of the micrometer at 0‘8000 inches and a 
temperature of 25°'0 C. Each value is the mean of three repetitions. 
Table I. 
Using first pair of faces 
Using second pair of faces 
Blocks in one 
position. 
cm. 
27-4106 
27-4103 
27•4085 
27-4100 
27-4088 
27-4093 
27-4087 
27-4083 
Blocks in reversed 
position. 
cm. 
27-4112 
27-4124 
27-4113 
27-4114 
27-4132 
27-4131 
27-4103 
27-4111 
Mean. 
cm. 
27-4109 
27-4114 
27-4099 
27-4107 
27-4110 
27-4112 
27-4095 
27-4097 
27-4105 
A second calibration was made at the end of the investigation to ascertain 
whether the gauge had been disturbed in any way by usage. This was done by 
means of a standardized pair of steel calipers. The results are tabulated below. 
Each figure represents the .mean of five settings. Although this method was not 
capable of the same accuracy as the first, it served as a very satisfactory check. 
Table II. 
Reading of the gauge 
in inches. 
Temperature of the 
gauge. 
Standard caliper Calculated value of 
reading for the same gauge set at 0-8000 inch, 
measurement. at 25° • 0 C. 
° C. 
cm. cm. 
0-8146 
29-0 
27-450 27•411 0 
0-7805 
29-0 
27-363 27-410 a 
0-8042 
29-1 
27-424 27 -411 6 
0-8191 
29-0 
27-460 27-409 6 
0-8097 
29-1 
27-437 27-410.4 
Mean. 27-410,; 
