Ban* STABILITY

505

Displacement Scale. (See plan of Caledonian Monarch.) The arm d% ty*

shall refer to later in greater detail.

(ii) Neutral Equilibrium.—When top weights are placed in the ship
so that her centre of gravity is raised gradually and approaches -M, the
arm GZ gets smaller and smaller and disappears altogether when 0
coincides with M. The downward force through G and the upward
force through B1 are then acting in the same vertical line; the lever has
disappeared and the ship is now in a condition of neutral equilibrium.

Fig. 27.

(iii) Unstable Equilibrium.—When the point G is above the meta-
centre we have the condition of unstable equilibrium and the arm G Z
operates a capsizing moment. The ship will heel over further and may
probably capsize.

Fig. 28.
The illustrations show that a ship is in (i) stable equilibrium when
Or is below M, a positive G M; (ii) neutral equilibrium when 6? coincides
with M; and (iii) unstable equilibrium when G is above M9 a negative
GM.
The foregoing principle of stability applies to small angles of heel
and is xeferred to as initial stability, which is the resistance offered by