FORCE OF THE WESTON NORMAL CELL IN SEMI-ABSOLUTE VOLTS. 
185 
trouble in regard to keeping the currents absolutely constant. It should be noted 
that the potentiometer corrections to the scale readings can be at once obtained from 
column four in the tables by dividing by 12’000.) 
(e) The Deflection Tables. 
In the first column an indication is given of the arrangement of the circuit. The 
different positions of the fixed coils are referred to as Positions I., II., III., and IV. 
where 
In Position I. we have 
Coil I. on west side of dynamometer with marked face out. 
,, II. ,, east ,, ,, ,, ,, ,, 
II. 
III. 
IV. 
,, I. ,, west 
„ II. ,, east 
5 ) 1 * )} }) 
,, II. ,, west 
,, I. ,, east 
,, II. ,, west 
5 5 
55 
in. 
5 > 55 55 
55 55 55 
,, ,, out. 
55 55 55 
A + and A— corresponds to a reversal of the current through the whole circuit. 
(The A represents the point so marked in fig. 6.) Changes from (l) to (3) or from 
(2) to (4) correspond to a reversal of the current through the fixed coils only, while a 
change from (l) and (3) readings to (2) and (4) means a reversal of the current 
through the suspended coils only if the current has not been reversed at A also. 
Observations (l) and (4) are always at the zero end of the scales, and (2) and (3) are 
always at the “hundred” end. In the reading marked A + (l), A + (3), A —(2), 
A—(4), the earth’s magnetic field acts to decrease S, while in A—(l), A—(3), A + (2), 
and A + (4) it acts to increase S. Wherever two consecutive readings (between 
groups) are not in opposite directions, it is due to the omission of a whole five- 
minute period in which it had not been possible to get all the auxiliary observations 
performed in time. 
In the second and third columns, the uncorrected telescope readings are given, and 
the fourth contains the potentiometer readings, a + value meaning that the drop in 
potential across the standard resistance was greater than the E.M.F. of the cell by 
the amount given. 
The fifth column contains the various temperatures t 1 of the standard two ohm 
coils at the time of the corresponding deflection; and t 2 represents the temperature of 
the two-tenths standard resistance in the circuit of the fixed coils. 
The value of half the average distance between the centres of the fixed coils “d,” 
is recorded in the next column. (See § III. ( b) for details of measurement), and the 
distance between the scales, (3 in the eighth column (see § VII. ( h )). 
VOL. CCXIV.—A, 2 B 
