with whom The Chief Justice joins, dissenting in part.
Georgia’s fourth exception concerns the islands in the Savannah River that came into existence after the States signed the Treaty of Beaufort in 1787. Agreeing with the Special Master, the Court finds these islands in South Carolina if they emerged on a portion of the riverbed belonging to *414South Carolina. Georgia contends that all islands formed by natural processes lie within its territory unless South Carolina has acquired them through prescription. I would sustain Georgia’s fourth exception and I therefore dissent from Part IV of the Court’s opinion and that portion of Part V concerning Oyster Bed Island.
The Treaty of Beaufort, in pertinent part, provides:
“ ‘The most northern branch or stream of the river Savannah from the sea or mouth of such stream to the fork or confluence of the rivers now called Tugoloo and Keowee, and from thence the most northern branch or stream of the said river Tugoloo till it intersects the northern boundary line of South Carolina . . . reserving all the islands in the said rivers Savannah and Tugoloo to Georgia . . . shall forever hereafter form the separation limit and boundary between the States of South Carolina and Georgia.’” Ante, at 381, n. 1 (emphasis added).
Georgia reasons that the clause reserving all islands to Georgia gives it sovereignty over all islands regardless of when or where they emerged. South Carolina maintains that the treaty placed the islands existing in 1787 in Georgia and then vested the rights of the two States with respect to the riverbeds. It contends that, under ordinary principles of property law, it has jurisdiction over any island that arose from its portion of the riverbed after that time. See St. Louis v. Rutz, 138 U. S. 226, 247 (1891). I agree with Georgia.
South Carolina’s view would render superfluous the clause “reserving all islands” to Georgia. The clause cannot give Georgia only the islands existing in 1787 because the treaty would give these islands to Georgia even in the absence of the clause. South Carolina lies to the north of Georgia. As a result, wherever the Savannah River contains islands, its northernmost streams flow between the islands and the South Carolina shore. All islands existing in 1787, therefore, lay on Georgia’s side of the dividing line and would belong to Georgia even if the treaty said nothing about islands. *415This is the principle of our decision in Georgia v. South Carolina, 257 U. S. 516 (1922). We ruled there that “the location of the boundary line ‘where the most northern branch or stream’ flows between an island or islands and the South Carolina shore” is midway “between the island bank on the one side and the South Carolina bank on the other.” Id., at 521-522. Consistent with this earlier holding, by interpreting the island reservation clause to address all islands regardless of when or where they arose, Georgia’s view gives effect to the language of the treaty.
Georgia’s rule also seems in keeping with what I think that the parties to such a treaty must have intended. When two States define their boundary according to a river, they may expect natural processes such as erosion and accretion to alter their borders. Louisiana v. Mississippi, 466 U. S. 96, 100 (1984); Arkansas v. Tennessee, 246 U. S. 158, 173 (1918). South Carolina takes the position that, although the boundary between the States moves when accretion and erosion change the river banks, the boundary does not change when these processes produce or alter an island within the river. Because the treaty defines the dividing line according to the most northern stream of the river, I do not think that those who signed it contemplated this uneven result.
Georgia’s position, in addition, comports better with our 1922 interpretation of the Treaty of Beaufort. In ruling on the status of islands in the Chattooga River (i. e., the most northerly branch of the Tugaloo River), our decree states that all of the islands belong to Georgia. See Georgia v. South Carolina, 259 U. S. 572 (1922). We saw no need, at that time, to distinguish islands that arose after 1787 from any other islands. See ibid, (distinguishing only those islands “formed by nature” from other islands). Even though we did not need to pass on the specific issue in this case in 1922, we should give some weight to the language of our previous order to avoid upsetting settled expectations.
The result advocated by Georgia seems quite reasonable. It has the benefit of simplicity because, so long as all islands *416belong to Georgia, one may discern the boundaries between the two States without knowing when the islands arose, how much they have eroded, or where the middle point of the river lay at the time of their emergence. Although the rule will favor Georgia in some instances, at other times it may work to the benefit of South Carolina. As Georgia explains in its brief:
“Either state stands to lose river bed as a result of natural changes in the river; likewise, each state has the potential of acquiring additional river bed as a result of accretion and erosion. For example, if an island existed in 1787 but was subsequently eliminated by gradual erosion, the boundary would be moved to the advantage of South Carolina, and river bed previously owned by Georgia would then be owned by South Carolina.” Ga. Exceptions 56 (footnote omitted).
For these reasons, I would sustain Georgia’s fourth exception.
Several consequences follow from my view. First, Oyster Bed Island would lie within Georgia’s territory, and the boundary would run north of the location adopted by the Court at this point in the river. See First Report of Special Master 88, n. 68 (noting that, if the treaty does place all islands in Georgia, “then the boundary line would definitely be north of Oyster Bed Island, and the Special Master is in error”). This conclusion prevents me from joining Part V of the Court’s opinion on this question.
Second, the small unnamed islands upstream and downstream from Pennyworth Island would belong to Georgia. My conclusion with respect to these islands prevents me from joining Part IV of the Court’s opinion.
Third, my interpretation of the treaty also implies that the Barnwell Islands which emerged after 1787 at one time belonged to Georgia. I agree with the Court, however, that Georgia lost these islands to South Carolina by prescription. I thus dissent in part.