PARALLELOGRAM OF FORGES

613

hand shroud, then tightened up from right to left, and finally the
other end is seized to the left hand shroud.

The next higher ratline is done in the same way, and they are
spaced 15 inches apart.

The Lansley Stress Finder comprises a set of movable metal scale
bars which can be set to solve the various parallelograms of forces
in connection with derrick work without calculation.

A B represents the mast which
is adjustable up or down to
suit the height of span above
the gooseneck.

B D the span or topping lift.
CD the derrick.
B E shows the stress on the

block at B.
D F gives the thrust on the

derrick.
C R is the stress on the heel

block at C.

The other arms show the various
component stresses involved.
• The makers are Messrs. Kelvin,
Bottomley and Baird, Glasgow.

PAINT.

^ t (See also page 480.)

Preparation of Surfaces.—All loose paint, rust, dirt and grease
should be removed from ironwork and the metal thoroughly dried
before applying the paint. The preparation of the material is of
groat importance to enable the paint to secure a firm grip on the
material by penetrating into the surface pores. Paint won't cling
to a dirty face.

Paint is usually sent on board ready mixed and only requires
stirring, and perhaps thinning with linseed oil and turpentine before
application. Red lead, however, is generally in powder, and if mixed
solely with oil the heavy pigment settles and forms a hard, solid
mass on the bottom of the container. This tendency is reduced
by first mixing the powder with water to form a stiff paste, then.