## A treatise on navigation and nautical astronomy |

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apparent altitude astronomical azimuth calculated celestial meridian centre chronometer showed compass course corr course and distance decl deviation diff dist earth east ecliptic equal altitudes equation equinoctial Examples feet given Greenwich date Greenwich mean heavenly body height of eye Hence horizon hour angle incr index correction Inman's Tables interval lunar magnetic course mean noon mean solar mean sun mean time nearly Mercator's chart meridian altitude meridian passage method miles minutes of arc moon moon's Nautical Almanac navigation observed altitude p.m. mean parallax parallel Parallel sailing plane point of Aries polar distance pole position prime vertical refraction represent Required the latitude rhumb line right ascension sailing semidiameter sextant ship mean ship's head sidereal sidereal day star star's subtract taken tide triangle true altitude true bearing true course true distance variation vers vessel zenith distance

### Popular passages

Page 117 - Mars a rather large pin's head, on a circle of 654 feet; Juno, Ceres, Vesta, and Pallas, grains of sand, in orbits of from 1000 to 1200 feet; Jupiter a moderate-sized orange, in a circle nearly half a mile across; Saturn a small orange, on a circle of four-fifths of a mile...

Page 133 - The angle of reflection is equal to the angle of incidence. 2. The incident and the reflected ray are both in the same plane, which is perpendicular to the reflecting surface.

Page 453 - AZIMUTH TABLES FOR THE HIGHER DECLINATIONS. (Limits of Declination 24° to 30°, both inclusive.) Between the Parallels of Latitude o° and 60°. With Examples of the Use of the Tables in English and French. By HB GOODWIN, Naval Instructor, Royal Navy. Royal 8vo.

Page 376 - A cos 6 = cos a cos c + sin a sin c cos B cos c = cos a cos 6 + sin a sin 6 cos C Law of Cosines for Angles cos A = — cos B...

Page 110 - The axis of a circle of a sphere is the diameter of the sphere which is perpendicular to the plane of the circle. The ends of the axis are called the poles of the circle.

Page 453 - ETC. ABBOTT.— ELEMENTARY THEORY OF THE TIDES: the Fundamental Theorems Demonstrated without Mathematics and the Influence on the Length of the Day Discussed. By TK ABBOTT, BD, Fellow and Tutor, Trinity College, Dublin. Crown 8vo.

Page 408 - The theoretical error of this method is very small, and the result thus obtained is decidedly to be preferred to the mere mean of the heights at high and low water. " The mean level thus determined is subject to meteorological influences, and it would be desirable, should there be an opportunity, to redetermine it at the same place at a different time of year. Should a regular series of observations for a fortnight be instituted, it would be superfluous to make an independent determination of the...

Page 158 - The apparent solar day is the interval between two successive transits of the sun's centre over the same meridian.

Page 164 - The sidereal time here given is that in common use among astronomers, and expresses the actual hour angle from the meridian, westward, of the true equinoctial point at the moment of observation. It is therefore affected by the equation of the equinoxes ; and is not, strictly speaking, a mean or uniformly increasing quantity. It ought, therefore, to be termed apparent sidereal time in the same manner as apparent solar time reckons from the actual arrival of the sun's centre on the meridian ; and in...

Page 424 - A Solar Day is the interval of time between two successive transits of the sun over the same meridian; and the hour-angle of the sun is called Solar Time.