( J7* ) 
€m move together ; fo that the Cavity I affign in rfie 
Earth, may well ferve to adjuft its weight to that of 
.the Moon. For other wife the Earth would leave the 
Moon behind it, and (he become another Primary Planet. 
But this I defign^to explain by a Difcourfe apart ijiore 
at large. 
F i &t I s. 
