MERIDIAN, one of the imaginary nr:i and south lines on the surface of the earth may be conceived of as passing through tcd poles and serving to indicate the longitude places, and with a parallel of latitude ma their exact position. If one conceive the are sliced into on one of these lines, the resalac surface is the plane of the meridian. The are also corresponding lines called astrcniamia or celestial meridian, which are imaginr circles of the celestial sphere passing throat the poles of the heavens and the zenith of in place on the earth's surface. These corregee exactly to the geographical meridians, that the celestial is exactly above the geographic= meridian of any place. Every pllaace on 6t globe has its meridian, and when the sun ar rives at this line it is noon or midday, wheat the name (Latin, meridianus — medius, mac and dies, day). (See LoscrrunE). The inn* venience arising from having a fixed =rib; in different countries is sufficiently obvious, au geographers, navigators and astronomers bite all found it frequently a source of conftrac. After years of fruitless discussion the questtot of a reference or first meridian for the worid came before an international conference at Washington, 1 to 22 Oct. 1884. There. it though the representatives of France 2-'0 Brazil dissented, it was agreed to reannsacz the meridian of Greenwich both as the astro nomical and as the geographical reference meridian of the world, longitude to he reck oned east and west from this up to 180°. At the same time it was advised that the astro nomical day should begin at midnight, mean Greenwich time, the hours for astronomical purposes being reckoned as before from 0 to 24. This arrangement began on I Jan. 1885.
Previously many foreign map-makers had ac cepted the meridian of Greenwich as first meridian, Germans and Americans apparently having no jealousy of Great Britain in regard to the matter. The change of time has had some importance for astronomers, hut ordinary civil time is still computed much as before. The zone system of reckoning standard time was adopted in the United States in 1883 and in Australia in 1895. In the former country there are four zones: the Eastern, taking time from the meridian of 75° W. (5 hrs. slow on Greenwich time); the Central, with standard meridian 90° W. (6 hrs. slow); the Mountain, 105° W. (7 hrs. slow); and the Pacific, 120° W. (8 hrs. slow). There are three Australian zones: Queensland, New South Wales, Victo ria and Tasmania, with 150° E. (10 hrs. fast) as standard; South Australia, with 135° E. (9 hrs. fast); and Western Australia, with 120° E. (8 hrs. fast). Other standards adopted with reference to Greenwich are: IS° E. (1 hr. fast) for Mid-Europe; 221/2° E. (PA hrs. fast) for Cape Colony; 30° E. (2 hrs. fast) for Natal; 135° E. (9 hrs. fast) for Japan; and 172%° E. (11% hrs. fast) for New Zealand. The merid ian is also applied to the laying out of the earth, magnetism on a chart, north and south line cutting the magnetic pole, or the vertical plane formed by such line is a magnetic merid ian. Consult any map for the meridian lines.