When the decimation is positive, the diurnal arc is longer than the nocturnal one; when the declination becomes negative the opposite relationship holds.

On this day, the sun which had risen at twenty minutes to six, set at forty minutes past five, having traced its diurnal arc for eleven hours above the horizon.

In astrology, a diurnal arc is the time, as expressed in right ascension, it takes a planet, point, or degree to move from its rising point to its setting point.

But once or twice, large shadows, veiling the sun, which described its diurnal arc through an extremely clear sky, indicated that a thick cloud of smoke passed between its disc and the island.

She was just starting to recover from the initial onslaught, when she made the rather serious mistake of trying to shake Tricia off by talking smoothly about diurnal arcs, right ascensions and some of the more abstruse areas of three-dimensional trigonometry.