ALLIPVION (Lat. allurio, a washing upon, from ad, to + lucre, to wash). The legal term for land gained from the sea or other waters, public or private, by the imperceptible relic tion of the water boundary or the gradual wash ing up of silt and earth, the scientific and pop ular term for which is alluvium. Alluvion is an accretion (q.v.) to the upland, and becomes part and parcel of the land to which it is annexed, and the property of the owner of the latter. When the change effected by the water is sudden, or so rapid as to be perceptible from day to day, as where the line of the seashore is altered by a storm, or a liter suddenly changes its course, or where the deposit, however gradual, is the intentional result of artificial causes, it is not an alluvion or accretion, and the title to the land so covered or uncovered is not affected. Thus, if the sea suddenly engulfs a tract of upland, the land continues to be the property of its former owner, even though it remain per manently submerged. The division of alluvion
between adjoining riparian proprietors, whose division line, if projected, would cut it, is a matter of some difficulty. Among several rules which have been adopted, the simplest is that which on private streams prolongs the division line at right angles with the middle line or thread of the stream. As such middle line is the boundary between opposite riparian proprietors, an island formed in the stream belongs to the proprietor on whose side of the line it lies. If this line cuts the island, the latter is divided by the line. Consult: Angell, Treatise on the Law of Watercourses (Boston, 1877) ; Gould, Treatise on the Lou' of Waters (Chicago, 1900). See AVULSION; RIPARIAN RIGHTS; SEASHORE; WA TER RIGHTS.