DICTIONARY OF

Speed of Wave______ __323______ ___Spiders Web
Speed of Wave. Rate at which successive crests pass a fixed point. In ocean waters, speed in
knots is approximately 0.8 speed of wind.
Speed Trial. The running of a vessel on a measured distance to ascertain her exact speed.
Spell. Time spent on a particular duty, or when relieved from duty.
Spencer. Loose-footed trysail set abaft mast and with head extended along a gaff.
Spencer Mast. Small mast, immediately abaft a principal mast, for carrying a trysail.
Spend. To spend a mast, spar, or sail is to cause it to be carried away in bad weather.
Sperm Whale. Alternative name for 'Cachalot'.
Sperry Gyro Compass. Electrically-driven gyroscope, revolving at about 9000 revolutions
per minute, that carries corrector devices for precessing it into the meridian and maintaining
it there. A 'phantom' follows all movements of axle relative to vessel's fore and aft line.
Sphere. Solid figure generated by half revolution of a circle about one of its diameters.
Spherical Aberration. Deviation of light rays from a focus after passing through curved
lens. Results in a coloured fringe caused by unequal refraction of lenses breaking up the light
into its constituent colours.
Spherical Angle. The inclination of one great circle to another. Can be measured by
intercepted arc of a great circle to which they are both secondaries, or by angle between lines
tangent to the circles at their point of intersection.
Spherical Sailing.* Methods of navigation that take into account the spherical shape of
Earth - instead of assuming a plane surface. Term is obsolete; methods are comprised in
great circle sailing.
Spherical Triangle. Area, on surface of sphere, bounded by arcs of three great circles.
Spheroid. Solid that is almost, but not quite, a sphere. Its section is an ellipse, and not a
great circle.
Sphinxer. Original name of a 'Spinnaker'.
Spica. Star Virginis. S.H.A. 159°; Dec. Sll°; Mag. 1-2. Name is Latin for 'Ear of Corn'.
Spica's Spanker. Four stars, in constellation Corvus, forming an irregular quadrilateral
resembling a spanker; the gaff pointing to Spica.
Spider. Iron band, around a mast, to take lower end of futtock rigging.
Spider Band. Iron band, around mast, for carrying belaying pins.
Spidereen Frigate. Fictitious vessel. A seaman who did not wish to give the name of his
ship used to say, 'The spidereen frigate with nine decks.'
Spider Hoop. Spider band.
Spider's Web. Spiders were formerly carried in surveying ships of Royal Navy as store
articles. Their purpose was to produce cross 'wires' for theodolites. Spider's Web Diagram,
a diagram consisting of a number of concentric circles and radii used for plotting radar and
tactical diagrams.