The Earth when nearest to the Sun, is in her _perihelion_; when most distant, in her _aphelion_.

The Moon, with regard to the Earth, is similarly in her _perigee_, and her _apogee_.
Analogous expressions denoting the relations of the Projectile towards the Moon, would be _periselene_ and _aposelene_.

At its _aposelene_ the Projectile's velocity would have reached its minimum; at the _periselene_, its maximum.

As it is to the former point that we are now moving, clearly the velocity must keep on diminishing until that point is reached.

Then, _if it does not die out altogether_, it must spring up again, and even accelerate as it reapproaches the Moon.