Note 64 — PART II. MOTION OF COMETS THROUGH THE SYSTEM.

Here it is important to remark, whether or not l′, l″ be greater than l. If they be each of them greater, the comet’s motion is direct; if less, retrograde. It may be noticed, that we already know from the values of r and r″, whether the comet is approaching or receding from the sun. If r″ be greater than r, of course it is receding.