The power of the archdeacon reached its zenith at the outset of the 1 3th century.
The pilgrimage, however, attained its zenith under Islam.
As the curtain approached, the compass needle always deviated to the west, oscillated as the curtain passed the zenith, and then deviated to the east.
At Tasiusak the auroral curtain after reaching the zenith usually retired in the direction from which it had come.
Furthermore, Gyllenskold says that when arcs mounted, as they not infrequently did, from the horizon, their apparent width might go on increasing right up to the zenith, or it might increase until an altitude of about 45° was reached and then diminish, appearing much reduced when the zenith was reached.