DICTIONARY OF

Semi-menstrual Inequality 302 Set the Watch
Semi-menstrual Inequality. Tidal inequality that goes through all its variations in half a
lunar month.
Sennit. Plaited yarns, strands, or ropes.
Senhouse Slip. Strong slip, secured to framing of ship in chain locker, to hold inboard end
of cable. Tumbler is shaped to pass through open link of cable and form a snug fitting for
link. Gives maximum strength when cable is veered to a clinch. Allows instant release when
required. Connection between ship and slip is by chain of such length that cable can be
slipped from deck immediately above chain locker.
Sensible Horizon. Plane of celestial sphere that is tangent to Earth at position of an
observer: is parallel to his rational horizon, and 4000 miles above it.
Sentinel. Electric apparatus in circuit of a navigation light, and causes a bell to ring if
filament of lamp fuses. 2. Apparatus formerly used in surveying vessels. Specially shaped
weight was towed over sea-bed by a wire from the stern. When depth varied, angle of wire
increased or decreased, and caused the bell to ring.
Separation. The means, or material, by which one parcel of a ship's cargo is separated from
another.
Separation Cloths. Large cloths used for separating different parcels of bulk cargoes such
as grain.
Separation Error. Error in the collimation of a sextant, or optical instrument.
Septentrional. Pertaining to the North. From the Greek for 'Seven ploughing oxen" (Ursa
Major).
Serein. Rain falling from a cloudless sky. Very abnormal.
Service. Serving put on a rope. 2. Duty performed. 3. Group of persons performing and
sharing the same duties.
Services. Royal Navy, Army, Royal Air Force.
Serving. Rendering service. 2. Small stuff tightly wound around a splice or rope to protect
it. 3. Act of putting on a serving.
Serving Board. Flat wooden tool used for serving a rope tightly and neatly.
Serving Mallet. Wooden mallet with a semi-circular groove along its cylindrically-shaped
head. Used for serving when considerable tension is desired.
Set. Direction in which a current flows.
Set and Drift. Direction and distance that a current travels in a given time.
Set Bolt. Bolt used for forcing another bolt out of its hole.
Set Flying. A sail set attached only by its halyard, sheet and tack but not by hanks to a stay.
Set Sail. To make sail. To loose sail and sheet home. 2. To sail away from a place.
Settee Rig. Boat rig having two masts, each carrying a four-sided fore and aft sail in which
the luff is much shorter than the leech.
Set the Watch. To name a watch and detail it for duty on deck.