indicator itself. Suppose, now, the vessel to be listed over to various
angles of heel--say 20 deg., 40 deg., 60 deg., and 80 deg.--the water
lines will then be A C, D E, F K, and H J respectively, and the centers
of buoyancy, which must be found by calculation, will be B1, B2, B3, and
B4. If lines are drawn from these points at right angles to the water
levels at the respective heels, the righting power of the vessel in each
position is found by taking the perpendicular distances between these
lines and the center of gravity, G. This method of construction is shown
to an enlarged scale in Fig. 2, where G is the center of gravity, B1
Z1, B2 Z2, B3 Z3, and B4 Z4 the lines from centers of buoyancy to water
levels; and G N, G O, and G P the distances showing the righting power
at the angles of 20 deg., 40 deg., and 60 deg. respectively, and which
to any convenient scale are set off as the ordinates in the stability
curve shown in Fig 3.

[Illustration: STABILITY INDICATOR FOR SHIPS. Fig. 1.]

Having obtained the curve, A, in this manner for a given metacentric
height, we will suppose that on the next voyage, with the same
displacement, it is found that, owing to some difference in stowage,
the center of gravity is 6 in. higher than before. The ordinates of the
curve will then be G N and G O--Fig.2--and the stability curve will
be as at C--Fig. 3--showing that at about 47 deg. all righting power
ceases. Similarly, if the center of gravity is lowered 6 in. on the
same displacement, the curve, B, will be found, and in this manner
comparative diagrams can be constructed giving at a glance the stability
of a vessel for any given draught of water and metacentric height.

[Illustration: STABILITY INDICATOR FOR SHIPS. Fig. 2.]