Territory — Water boundaries — Interpretation of boundary treaty — Boundary formed by north channel of river — Effect of islands emerging after conclusion of treaty — Use of right-angle principle in delimitation — Boundary at mouth of river — Location of mouth of river in absence of specific geographical headland — Avulsion — Additions to island mass occurring over time as result of engineering works — Effect on boundary — Lateral seaward boundary — Equidistance principle — Treaty of Beaufort, 1787

Territory — Acquisition of — Prescription — States of American Union — Boundary rivers — Boundary treaty giving all islands to Georgia — South Carolina exercising sovereignty over islands — Effect of inaction by Georgia

Treaties — Interpretation of boundary treaty — Boundary formed by north channel of river — Islands emerging after treaty — Whether treated as pre-existing — Whether determination of sovereignty over islands consistent with treaty — Demarcation of seaward boundary — Whether demarcation consistent with treaty — Treaty of Beaufort, 1787 — The law of the United States