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See also: body from the meridian, as measured around the See also: celestial See also: pole
.
It is equal to the angle at the pole between the See also: hour circle through the body and the meridian, but is usually expressed in See also: time
.
HOUR-See also: GLASS, a See also: device for measuring intervals of time, also known as See also: sand-glass, and as log-glass when used in conjunction with the See also: common log for ascertaining the See also: speed of a See also: ship
.
It consists of two See also: pear-shaped bulbs of glass, See also: united at their apices and having a minute passage formed between them
.
A quantity of sand (or occasionally of mercury) is enclosed in the bulbs, and the See also: size of the passage is so proportioned that this sand will completely run through from one bulb to another in the time it is desired to measure—e.g. an hour or a minute
.
See also: Instruments of this kind, which have no See also: great pretensions to accuracy, were formerly common in churches
.
In the See also: English See also: House of See also: Commons, as a preliminary to a division, a two-minute sand-glass is still turned, and while the sand is See also: running the " division bells " are set in motion in every See also: part of the See also: building, to give members See also: notice that a division is at See also: hand
.
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