Schematic PV diagrams of a cone with its top (northern) part tilted towards us. Top panel: cut perpendicular to the cone axis showing the elliptical PV diagram through the cone. Bottom panel: cut along the cone major axis. We show two simplified cases: the straight solid lines show the PV diagram of outflowing gas along the cone walls of constant velocity. The dashed lines show the generic PV diagram along the axis of a cone where the gas is first linearly accelerating and then decelerating to zero velocity.