HOW IS SHE HEADING f 221

TO FIND OUT HOW ANOTHER VESSEL IS HEADING.
A vessel's side-lights are screened to show the light from right ahead
fco 2 points abaft her beam (See further note on screening of side-lights,
page 256.)
When the side-light of another vessel is cut off from view, or is
just coming into sight, it indicates that the observer is bearing 2 points
abaft her beam. From this information the direction in which the
other vessel was heading at the moment can be ascertained as follows:—
A BED light just being shut out'will indicate that the vessel carrying it
was heading 6 POINTS TO THE LEFT of its bearing, because red is the
left hand light.
A GREEN light being just shut out will indicate that the vessel
carrying it was heading 6 POINTS TO THE RIGHT of its bearing, because
green is the right hand light.
The rule has nothing whatever to do with the direction the observer's
vessel is heading, unless the bearing of the other ship is given as so
many points on the bow, when, of course, he must know how his vessel
is heading in order to get the bearing of the light.
In Diagram 1 the observer must imagine himself to be in the centre
of the compass, which represents the centre of his horizon, and that the
side-light of each of the vessels Nos. 1 to 6 is just being shut out on the
respective bearings as indicated, it is required to know how each vessel
was heading.
V.
1. Green light shut out when bearing Northl
Six points to right of the bearing—B.N.B.
% Bed light shut out when bearing N.E.?
Six points to left of the bearing—N.N.W.
3, Green light shut out on an E.S.E. bearing?
She is heading South.
4. Red light disappears on a S.S.E. bearing?
She is heading East.
5. Green light disappears on a S.W. bearing?
She is heading W,N.W.
6, Red light shut out when bearing W.N. W.1
• " She is heading S.W,