from
Bouvier's Law Dictionary, Revised 6th Ed (1856)
UNITY OF POSSESSION. This term is used to designate the possession by one
person of several estates or rights. For example, a right to an estate to
which an easement is attached, or the dominant estate, and to an estate
which an easement encumbers, or the servient estate, in such case the
easement is extinguished. 3 Mason, Rep. 172; Poph. 166; Latch, 153; and vide
Cro. Jac. 121. But a distinction has been made between a thing that has
being by prescription, and one that has its being ex jure naturae; in the
former case unity of possession will extinguish the easement; in the latter,
for example, the case of a water course, the unity will not extinguish it.
Poth. 166.
2. By the civil code of Louisiana, art. 801, every servitude is
extinguished, when the estate to which it is due, and the estate owing it,
are united in the same hands. But it is necessary that the whole of the two
estates should belong to the same proprietor; for if the owner of one estate
only acquires the other in part or in common with another person, confusion
does not take effect. Vide Merger.