As will be seen from diagram, [Fig. 1], Pl. xxiv., the proportion between the unknown resistance X, and the artificial resistance n is, when the deflection is read off on the side of the slate disc marked A:
| X | : n | = | 150 + a | : 150 - a | |
| or, | X | = | 150 + a | · n. | |
| 150 - a | |||||
but if read off on the B side of the disc—
| X = | 150 - a | · n. |
| 150 + a |
The values of these two fractions, for every half degree, will be found in the columns headed A and B of the table in the Appendix.
SIEMEN'S UNIVERSAL GALVANOMETER.
SIEMEN'S UNIVERSAL GALVANOMETER.