502

NICHOLLS'S SEAMANSHIP AND NAUTICAL KNOWLEDGE

wHen the vertical line falls outside the base. The broader its base
the more stable will the block of wood be The same principle applies
to a person who is losing his balance but spreads out his legs to prevent
himself from falling by broadening out his base of support.

The equilibrium of a floating ship is somewhat similar but not
quite the same owing to the difference in the density of the medium
which supports her. The block of wood is supported at the surface
of the table, a ship is supported by, but not at the surface of, the water.
Displacement-Tonnage is the weight of the ship and her contents
in actual avoirdupois tons

Volume of Displacement is the quantity of water required to fill
the moulded shape of the hole left by the ship if she were lifted out of
the medium in which she floats. The weight of the water is equal to
the weight of the ship, but the volume of the water is only equal to
the volume of the underwater portion of the ship. The displacement
may be expressed in convertible terms, either in tons weight or in
measured capacity.

1 ton fresh water =36 cubic feet

1 ton salt water =35 cubic feet

The displacement tonnage can be found by multiplying the product
of the vessel's length, breadth and mean draft by her coefficient of
fineness; this gives the volume of displacement in cubic feet, and as
there are 35 cubic feet of sea water to a ton, by dividing this volume
by 35 we obtain the displacement tonnage, thus:

Displacement tonnage L X B X d x coefficient

in sea water

35

Fjg. 24.
Coefficient of Fineness.—The coefficient of fineness of a vessel is the
ratio or proportion her underwater form bears to a rectangular shaped
block of the same length, breadth and depth (Figure 24).
It will be realised, therefore, that the finer lines a vessel has the