DICTIONARY OF

Zone of Silence 393 Zygaena
Zone of Silence. Area in which a sound is inaudible although it may be heard all round the
area. The cause of it is not known. Quite frequently noticed in connection with fog signals of
lighthouses.
Zone Time. Time kept at sea for official purposes. Sea areas are divided into sectors (termed
'zones') that extend 7° on either side of the prime meridian, and of all meridians of 15° or a
multiple of it. Each zone keeps a time that is one hour different from the zone on either side
of it. Each zone, therefore, has a time that is an integral number of hours different from
Greenwich Mean Time, and the zone is named by this number. Easterly zones prefix a minus
sign, westerly zones prefix a plus sign, to the zone number. The zone number, when applied
to the zone time, and using its prefixed sign, will give Greenwich Mean Time. Zone+12 and
zone -12 meet at the Date Line.
Zubenelg. Star Librae. S.H.A. 131°; Dec. S09°; Mag. 2.7.
Zubenelgenubi. Star a Librae. S.H.A. 138°; Dec. S16°; Mag. 2.9.
Zubenesch. Old name for star a Lyrae.
Zugites. The middle tier of oarsmen in an ancient Greek trireme.
Zulu. Scottish east coast fishing vessel.
Zygaena. The genus to which the hammer-headed shark (Zygaena malleus) belongs.