Section 3 Only two liferent provisions to be subsisting at one time.

Provided always, that where two liferents to wives or husbands, granted under the powers herein before contained, shall be subsisting at any one time upon an entailed estate, it shall not be competent to grant a third liferent to take effect till one of the former subsisting liferents shall cease or expire; but the power of granting a liferent may be exercised so as to increase a former liferent, or grant a new liferent to the extent herein-before authorized to be granted, upon the ceasing or expiration of any former or subsisting liferent, although the same may not take place in the lifetime of the person granting such prospective or increased liferent.