The metals may be arranged in a series according to their power of displacing one another in salt solutions, thus Cs, Rb, K, Na, Mg, Al, Mn, Zn, Cd, Tl, Fe, Co, Ni, Sn, Pb, (H), Sb, Bi, As, Cu, Hg, Ag, Pd, Pt, Au.
Assuming, for example, that the northern star has the smaller right ascension, the instrument is first, with the aid of the stop, placed in the meridian towards the north; the verniers of the graduated circle g are set to read to the reading 40-2(Sn+Ss) where 0 is the approximate latitude of the place and Sn, Ss the declinations of the northern and southern star respectively; then the level frame h is turned till the levels k and I are in the middle of their run, and there clamped by the screw m, aided in the final adjustment by the adjoining slow motion screw shown in the figure.
If V denote the potential, F the resultant force, X, Y, Z, its components parallel to the co-ordinate axes and n the line along which the force is directed, then - sn = F, b?= X, - Sy = Y, -s Surfaces for which the potential is constant are called equipotential surfaces.
The most important cases are I +2 +3 +...+n = 2n(n +I), 12+22+32+...+n2 = sn(n+I) (2n+1), I 3 +2 3 +3 3 +...
They have also formed in this way certain alloys of definite composition, such as AuCd 3, Cu 2 Cd, and, more interesting still, Cu 3 Sn.