224 NICHOLLS'S SEAMANSHIP AND NAUTICAL KNOWLEDGE

4. A. Both side-lights bearing S.W.? She is heading N.B.

B. Green light bearing S.W.? She is heading between W.N.W and
N.B.

C. Eed light bearing S.W.1 She is heading between S.S.B. and N.E.
6. A. Both lights bearing W N.W.I She is heading E.S E.

R Green light bearing W.N.W.? She is heading between North
and E.S.E.

C. Eed light bearing W.N.W.? She is heading between S.W. and
E.S.E.

The angle of parallax subtended by the two masthead lights of a
steamship gives a good idea of the direction she is heading. When one
light is vertically over the other she is approaching end on; when the
lower light is to the right of the higher one she is crossing over to star-
board and when the lower light is to the left of the higher one she is
crossing over to port.

A square-rigged vessel cannot head closer to the direction of the
wind than 6 points, that is to say, the wind is 6 points on her starboard
bow when she is on the starboard tack and 6 points on her port bow
when she is on the port tack, so that there is always an arc of the horizon
of 12 points on which she cannot make headway. '

A sailing vessel in fog gives One blast when on the Starboard ta^k;
Two Blasts when on the Port tack, and Three blasts when she has the
wind Abaft the Beam, She gives the close-hauled signal when the wind
is exactly abeam, and when changing from one tack to th,e other she
continues to give the fog signal for the last tack she was on until she
has headway on her new tack.

(i) <n) <'{m) (H) IV)

Fig. 4.

Ewmples — in fog —
(i) Wind North, a sailing vessel giving 1 blast, how is she heading!

(i!) Wind North, a sailing vessel giving 2 blasts; how is she heading?
B.N,BL '
Wind North, a sailing vessel giving 3 Waste; how is she headisgf
Fjrom East to West by way of South.