mid-channel

The middle of a navigable stream. 56 Am J1st Wat § 177. Grotius and Vattel speak of the middle of the river as the line of demarcation between two jurisdictions, but modern publicists and statesmen prefer the more accurate and more equitable boundary of the navigable mid-channel. If there be more than one channel of a river, the deepest channel is regarded as the navigable mid-channel for the purpose of territorial demarcation; and the boundary line will be the line drawn along the surface of the stream corresponding to the line of deepest depression of its bed. The islands on either side of the mid-channel are regarded as appendages to either bank; and if they have once been taken possession of by the nation to whose bank they are appendant, a change in the mid-channel of the river will not operate to deprive the nation of its possession, although the water-frontier line will follow the change of the mid-channel. Iowa v Illinois, 147 US 1, 9, 37 L Ed 55, 58, 13 S Ct 239.