That increase of the earth on a shore or bank of a river, or to the shore of the sea, by the force of the water, as by a current or by waves, which is so gradual that no one can judge how much is added at each moment of time. Inst. 1, 2, L 1, 8 20. Ang. Water Courses, 53. Jefferis v. East omaha Land Co., 134 U. S. 178, 10 Sup. CL 518, 33 L. Ed. 872; Freeland v. Pennsylvania R. Co., 197 Pa. 529, 47 Atl. 745, 58 L. R. A. 206. 80 Am. St. Rep. 850