DICTIONARY OF

Circle of Position 82 Clack Valve
Circle of Position. Small circle on surface of Earth, and on the circumference of which an
observation shows observer to be.
Circle of Right Ascension. Great circle of celestial sphere, passing through all points
having the same right ascension.
Circle of Sphere. Formed by intersection of a sphere by a plane. May be 'great circles' or
'small circles', depending on whether the plane does, or does not, pass through centre of
sphere.
Circle of Tangency. 'Tangent Circle'.
Circuit. Series of connected conductors that form a path for an electric current.
Circular Note. Letter of credit addressed to financial firms in other countries. Authorises
them to make payment to person named.
Circular Parts. 'Napier's Circular Parts‘
Circular Sailing.* Former name for 'Great circle sailing'.
Circular Storm.* Former name for a cyclonic storm.
Circulating Pump. Centrifugal, or double-acting pump, that draws water from sea and
delivers it at external surfaces of condenser tubes, so condensing exhaust steam from
engines.
Circulation. Process by which water in a boiler is moved so that the whole mass is of
uniform temperature. Partly done by convection, but hastened by pump and special fittings.
Circummeridian. About or near the meridian.
Circumnavigate. To sail completely around. Sometimes especially applied to sailing
around Earth.
Circumnavigator's Day. The day 'lost' or 'gained' by the navigator when date is altered on
crossing the Date Line on W'ly or E'ly course (respectively).
Circumpolar. Term applied to a heavenly body that makes a diurnal revolution around
pole of heavens without passing below horizon.
Cirrocumulus. An intermediate form of cloud often called 'Mackerel sky'. Formed by
small, rounded masses of cloud.
Cirrostratus. High, tenuous cloud of uniform density. Often precedes a depression.
Cirrus. Feathery, fibrous, detached clouds, white in colour, that are formed by ice crystals
at heights of five to seven miles.
Cirrus Nothus. 'False Cirrus.'
Cistern. The mercury container of a barometer. Pressure of atmosphere in cistern forces
mercury up the glass tube that has been exhausted of air.
Civil Day. Period from midnight to midnight in the mean time standard at a given place.
Civil Twilight. Interval between Sun's upper limb being in horizon, and his centre being 6°
below it.
Civil Year. The year in common use. Is the Tropical year adapted for civil purposes.
Has 365 days for three years and 366 in fourth with slight adjustment at ends of centuries.
Clack Valve. Hinged valve that opens by suction and closes by gravity.