160. A future estate is one which does not entitle its owner to the possession of the land until some time in the future. Future estates, according to the source to which they are to be referred, are:
(a) Those possible at common law (p. 279).
(b) Those arising under the statute of uses (p. 298).
(c) Those arising under the statute of wills (p. 300).
The estates which have been considered so far have been, for the most part, estates which entitle their owners to the immediate possession of the land in which the estate exists; that is, they have been present estates. However, mention has been made incidentally, in several places, of future estates, or estates which do not entitle their owners to immediate possession. A future estate is what remains of a fee simple after some present estate of a less quantity has been carved out of it. It is the difference between a fee simple and a fee tail, or a fee simple and a life estate, etc. When the present estate comes to an end, the future estate takes effect in possession, and becomes a present estate.