FORCE OF THE WESTON NORMAL CELL IN SEMI-ABSOLUTE VOLTS. 
191 
in this case t = 3|- minutes, T = 5 minutes, and it was found that D = 0'049 cm. and 
k = 0'22. Hence x = 0‘0149 cm. This is for a single deflection, and therefore for S 
we must subtract 0'0298 cm. 
(g) The Final Value of S. 
We have to apply the above corrections. 
(1) + 0"0008 cm. 
(2) +0T014 „ 
(3) +0-0013 „ 
(4) -0-0298 „ 
Total -0'0263 „ 
The final value of S was therefore 
84 f 629 7 cm. 
(h) The Determinations of /3, the Distance between the Scales. 
This distance was measured by means of a rigid brass tube which was fitted with 
micrometer calipers at one end, and with an end stud at the other. The distance 
between the faces of the scales was determined directly by placing the end-stud against 
one scale, and the micrometer was so attached that it could be screwed against the 
face of the other scale. The temperature could be obtained from two thermometers 
which were inserted about 50 cm. from each end, respectively, and the tube was bound 
with thick asbestos cord to provide handling places. 
The tube was calibrated on the standardized fifty-foot comparator at the Macdonald 
Engineering Building, McGill University. The method adopted was similar to that 
described in § III. (6), for the calibration of the smaller instrument used for determining 
the distance between the fixed coils. The following results were obtained for different 
calibrations. The figures given are reduced to the value of the length with the 
micrometer set at 0"300 cm. at a temperature of 20°"0 C., 
117"503 inches, 
117-505 „ 
117-505 „ 
117-504 „ 
Mean . . . 117‘504 „ fie., 29S^O cm. 
The scale distance was determined before and after each deflection series. It was 
found that the water circulation through the supporting pipes kept this quite constant. 
