DICTIONARY OF

Chromosphere 81 Circle of Perpetual Occultation
Chromosphere. Incandescent gaseous envelope surrounding Sun.
Chronograph. A watch combined with a stop-watch mechanism.
Chronometer. Very accurately constructed timepiece with a balance wheel of a form that
precludes error through change of temperature. Balance wheel is affected by mainspring for
only a very small period of its oscillation. Invented by John Harrison about 1728.
Chronometer Journal. Book for recording comparisons of chronometers carried in a ship.
Shows their error on time signal, and on each other. Daily rates, also, are deduced and
entered.
Chronometer Watch. Small timepiece made on chronometer principle and used for taking
times on deck.
Chronometric Difference. Difference of longitude between two places when expressed as
the difference of their local mean times.
Chuch. Name sometimes given to a fairlead.
Chutes. Inclined troughs, down which coal, ashes and fluid substances can slide. 2. Vertical
canvas tubes used for ventilating. Often spelt 'shoots'.
Circle. Plane figure bounded by a line that, at all points, is equidistant from a point termed
the 'centre'. Can be considered as the section of a sphere by a plane. Word is frequently
applied to its circumference, as in 'position circle'.
Circle of Altitude. Great circle of celestial sphere, secondary to horizon, on which altitudes
are measured.
Circle of Azimuth. Great circle of celestial sphere passing through zenith; so passing
through all points having the same azimuth.
Circle of Curvature. Circle whose curvature is the same as that of a curve under
consideration.
Circle of Declination. Great circle of celestial sphere that is perpendicular to Equinoctial.
So called because declination is measured along it. Not to be confused with 'Parallel of
Declination'.
Circle of Equal Altitude. Circle, on surface of Earth, passing through all positions at which
the body has the same altitude. It is a great circle when body is in horizon, decreasing to a
point when body is in the zenith.
Circle of Excursion. Small circle, parallel to Ecliptic, marking the maximum celestial
latitude of a planetary body.
Circle of Illumination. Great circle, on surface of Earth, that divides day from night.
Circle of Latitude. Alternative name for a circle of celestial longitude. So named because
latitude is measured on it.
Circle of Longitude. Great circle of celestial sphere, secondary to Ecliptic, passing through
all points having the same celestial longitude.
Circle of Perpetual Apparition. Parallel of declination, above which all the diurnal circles
are entirely above horizon.
Circle of Perpetual Occultation. Parallel of declination, below which all the diurnal circles
are entirely below horizon.