ME. LATIMEE CLAEK ON A STANDAED VOLTAIC BATTEET. 
i 
electromotive force (E) follows from Ohm’s formula, 
C=§ or E=CR. 
In the instrument in question (fig. 2) the large fixed coil is double, as in the arrange- 
Fig. 2. 
ment given by Helmholtz and Gaugain to the tangent galvanometer, the two coils being 
in parallel vertical planes at a distance apart equal to their radius ; the small coil is also 
