The verge (or crown wheel) escapement is the earliest known type of mechanical escapement, the mechanism in a mechanical clock that controls its rate by allowing the gear train to advance at regular intervals or 'ticks'.he verge (or crown wheel) escapement is the earliest known type of mechanical escapement, the mechanism in a mechanical clock that controls its rate by allowing the gear train to advance at regular intervals or 'ticks'.
You need the foci for some construction methods. Just draw radii of length a from the ends of the minor axis. Given the foci, however, you can't uniquely determine the axes. You need additional information such as the length of one axis.
Construct the locus of a point P at a constant distance of 2 cm from a fixed point Q. Construct a circle with center Q and radius 2 cm. Locus formed: A perpendicular bisector of the line XY. Construct the locus of point P moving equidistant from fixed points X and Y and XY = 6 cm.