_But I call that Body more grave absolutely than this, if that
weigh more than this, without any respect had to the Masses._
And thus a great piece of Wood is said to weigh more than a little
lump of Lead, though the Lead be _in specie_ more heavy than the Wood.
And the same is to be understood of the less grave _in specie_, and
the less grave absolutely.
These Termes defined, I take from the Mechanicks two Principles: the
first is, that