The surveyor's compass is an instrument for determining the horizontal direction of a line with reference to the direction of a magnetic needle.    The compass is set over a point on the line of the bearing which is desired and the compass is leveled.  The peep sights are directed to some point along the line, and the needle is lowered on to the pivot.  The bearing is determined by observing the angular value on the graduated scale opposite the end of the needle, and the quadrant is determined by observing between which letters on the compass-box the end of the needle lies.