“ The qualification annexed to the grant of an estate or interest in land, providing for the determination of that grant or interest upon a particular contingency happening. An estate with such a limitation can endure only until the particular contingency happens; it is a present interest, to be divested on a future contingency. The grant of an estate to a man so long as he is parson of Dale, or while he continues unmarried, are instances of conditional limitations of estates for life. (2) A future use or interest in land limited to take effect upon a given contingency. ”