¹ See historical review by E. Nys, in his Le Droit International, I, 423-437, citing at 424, H. Helmolt, in the Historisches Jahrbuch, 1896, pp. 235 et seq.

² Ibid., I, 425.

³ Campbell’s Grotius, Chapter III, §§ 7 and 8; Chitty’s Vattel (1859), Chapter XXII, § 266, p. 120.

⁴ See E. Engelhardt, Du Régime Conventionnel des Fleuves Internationaux, 73.

⁵ See Article 6 of Treaty of Luneville, February 9, 1801, De Clercq, Traités de la France, I, 426, following the views by the French plenipotentiaries expressed at the Congress of Rastadt in March and April, 1798.

⁶ Numerous treaties since the beginning of the nineteenth century make express provision that the frontier along navigable rivers shall follow the thalweg. See, for example, Art. V of the definitive treaty between France and the Allies of May 30, 1814, Brit. & For. State Pap. I, Pt. I, 156; also collection of treaties containing similar provisions in the Argument of the United States in the Chamizal Arbitration (Washington, 1911) 10-21. Among recent conventions to the same effect may be noted that between the Argentine Republic and Brazil of October 6, 1898, Brit. & For. State Pap., XC, 85; also that between Great Britain and France of June 14, 1898, for the delimitation of possessions west of the Niger, Brit. & For. State Pap., XCI, 38, 45.

The treaties of the United States concerning river boundaries lack uniformity of expression. Article II of the definitive treaty of peace with Great Britain of September 3, 1783, provided that the frontier should follow the “middle” of boundary rivers as well as of water communications between the lakes. (Malloy’s Treaties, I, 587.) Article I of the Webster-Ashburton treaty of August 9, 1842, provided that the frontier along the river St. John should follow the “middle of the main channel.” (Id., I, 651.) The treaty of April 11, 1908, concerning the Canadian international boundary, provided in Article II, respecting the St. Croix River, that the line should “follow the center of the main channel or thalweg as naturally existing, except where such course would change or disturb or conflict with the national character of islands as already established by mutual recognition and acquiescence.” (Id., I, 818.) This is the first boundary convention of the United States in which the term thalweg was employed.

Article II of the treaty with Spain of October 27, 1795, provided that the boundary along St. Mary’s River should follow the “middle thereof;” while Article IV declared that the “western boundary of the United States which separates them from the Spanish colony of Louisiana is the middle of the channel or bed of the river Mississippi.” (Id., II, 1641, 1642.) Article III of the treaty with Spain of February 22, 1819, provided that the boundary should follow the “course” of the Red River between specified points, all islands therein being assigned to the United States. (Id., II, 1652-1653.)

Article II of the treaty with Mexico of January 12, 1828, declared that between specified points the boundary should follow the “course” of the Rio Roxo or Red River. (Id., I, 1083.) According to Article V of the treaty of Guadaloupe-Hidalgo, of February 2, 1848, the boundary was to proceed up the “middle” of the Rio Grande “following the deepest channel where it has more than one;” also down the “middle” of a specified branch of the river Gila. (Id., I, 1109.) Article I of the Gadsden treaty with Mexico of December 30, 1853, referred to the “middle” of the Rio Grande, and likewise to that of the Colorado. (Id., I, 1122.) In the preamble of the boundary convention with Mexico of November 12, 1884, it was declared that according to the provisions of the two last mentioned treaties the dividing line follows the “middle of the channel of the Rio Grande and Rio Colorado;” and it was therefore provided in Article I, that the dividing line should forever “follow the center of the normal channel of the rivers named, notwithstanding any alterations in the banks or in the course of those rivers, provided that such alterations be effected by natural causes through the slow and gradual erosion and deposit of alluvium and not by the abandonment of an existing river bed and the opening of a new one.” (Id., I, 1159-1160.)

⁷ Declares Westlake: “When a river forms the boundary between two states it is usual to say that the true line of demarcation is the thalweg, a German word meaning literally the ‘downway,’ that is the course taken by boats going down stream, which again is that of the strongest current. The slack current being left for the convenience of ascending boats. Thal in the sense of valley enters into thalweg only indirectly. The immediate origin of the word lies in the use of berg and thal to express the upward and downward directions on a stream, like amont and aval in French.” (Int. Law, I, 141, and note 1.)

Declared the Supreme Court of the United States in the case of Louisiana v. Mississippi, 202 U. S. 1, 49: “The term ‘thalweg’ is commonly used by writers on international law in definition of water boundaries between States, meaning the middle or deepest or most navigable channel. And while often styled ‘fairway’ or ‘midway’ or ‘main channel,’ the word itself has been taken over into various languages. Thus in the treaty of Luneville, February 9, 1801, we find ‘le Thalweg de l’Adige,’le Thalweg du Rhin,’ and it is similarly used in English treaties and decisions, and the books of publicists in every tongue.” According to Article III of the “Plan respecting the International Regulation of Navigable Rivers,” adopted by the Institute of International Law at Heidelberg, in 1887, ‘the frontier of the states separated by the rivers is marked by the thalweg, that is to say by the medial line of the channel.” (Annuaire, IX, 182.)

⁸ See Sir G. S. Baker’s 4th ed. of Halleck’s Int. Law, 182, § 23.

⁹ See Iowa v. Illinois, 147 U. S. 1, 7-14; Handli/s Lessee v. Anthony, 5 Wheat. 374; Buttenuth v. St. Louis Bridge Co., 123 III. 535; Keokuk & Hamilton Bridge Co. v. The People, 145 111, 596; Same v. Same, 167 111. 15; Keokuk & Hamilton Bridge Co. v. Illinois, 175 U. S. 626; Bellefontaine Improvement Co. v. Niedringhaus, 181 111. 426; Louisiana v. Mississippi, 202 U. S. 1; Iowa v. Illinois, 202 U. S. 59. Compare, opinion of Mr. Crittenden, Attorney-General, 5 Op. Attys.-Gen., 412.

The Supreme Court of the United States, in the case of Iowa v. Illinois (147 U. S. 1, 7-14), has declared that, according to international law and the usage of European states, the terms “middle of the stream” and the “mid-channel” as applied to a navigable river, are synonymous and interchangeably used; and that the former was employed in the latter sense in the treaty of peace concluded by Great Britain, France and Spain at Paris in 1763. It may be doubted whether the quotations made from Wheaton, Creassy, Twiss, Halleck, Woolsey and Phillimore, sustain such a conclusion. It is believed that prior to the Treaty of Luneville of 1801, nations employed the term “middle of the stream” or “mid-stream” in boundary conventions for the reason that a line other than one drawn mid-way between the banks of a river was rarely contemplated. After that treaty, states having become familiar with the principle of thalweg, seem to have employed either that term or some other clearly synonymous with it whenever the new mode of demarcation was intended. The principal boundary treaties concluded since the beginning of the nineteenth century afford abundant evidence of the fact that states have generally taken great care to express their acceptance of the principle of thalweg, and have avoided the use of words the literal meaning of which might encourage the inference that the contracting parties sought to retain the old method of establishing a frontier.

¹⁰ See opinion of Mr. Cushing, Attorney-General, 8 Op. Attys.-Gen., 175; Nebraska v. Iowa, 143 U. S. 359; McBaine v. Johnson, 155 Missouri, 191; Bellefontaine Improvement Co. v. Niedringhaus, 181 Illinois, 426; Argument of the United States in the Chamizal Arbitration, p. 26.

See also Article I of the boundary convention between the United States and Mexico, of Nov. 12, 1884, which is believed to express with exactness the correct rule of law in the requirement, that in order to subject the boundary to variations of the thalweg, the changes in the latter must be “effected by natural causes.” (Malloy’s Treaties, I, 1159-1160.)

In the case of Washington v. Oregon, 211 U. S. 127, 136, the Supreme Court of the United States declares: “When, in a great river like the Columbia, there are two substantial channels, and the proper authorities have named the center of one channel as the boundary between the States bordering on that river, the boundary, as thus prescribed, remains the boundary, subject to the changes in it which come by accretion, and is not moved to the other channel, although the latter in the course of years becomes the most important and properly called the main channel of the river.”

¹¹ See opinion of Mr. Cushing, Attorney-General, 8 Op. Attys.-Gen. 175; Cooky v. Golden, 52 Mo. App. 229; Nebraska v. Iowa, 143 U. S. 359; Missouri v. Nebraska, 196 U. S. 23; Buttenuth v. St. Louis Bridge Co., 123 111. 535, 546.

¹² In the case of Nebraska v. Iowa, 143 U. S. 359, the Supreme Court of the United States held that while there might be an instantaneous and obvious erosion on one side of the Missouri River, if the accretion to the other side was gradual and imperceptible by alluvial deposits, the boundary would follow the changes in the channel thus effected, notwithstanding their rapidity.

In the case of the Chamizal Arbitration before the Special International Boundary Commission, under the convention between the United States and Mexico of June 24, 1910, a grave problem arose concerning the interpretation of the boundary convention between those countries of November 12, 1884, relating to the Rio Grande and Rio Colorado. Article I of that convention provided that the dividing line should follow the center of the normal channel of those rivers irrespective of any alterations in their banks or courses, provided that such alterations were “effected by natural causes through the slow and gradual erosion and deposit of alluvium and not by the abandonment of an existing river bed and the opening of a new one.” The presiding commissioner, Professor La Fleur, and the Mexican commissioner, Mr. Puga, who constituted a majority of the tribunal, were of opinion that the language quoted signified that the boundary should not vary with alterations in the course of the Rio Grande in case of a rapid and obvious erosion even though there might be no abandonment of the river bed. The American commissioner, General Mills, was, however, of opinion that it was impossible to impute to the contracting parties an intention to prevent the boundary from following changes in the course of the river in the case of rapid and perceptible erosion unless there was also an abandonment of the existing river bed. For the text of the award of the court and the dissenting opinion of the American commissioner, see this Journal, Vol. 5, p. 782.

¹³ Handly’s Lessee v. Anthony, 5 Wheat. 374,

Writes Hall: “Upon whatever grounds property in the entirety of a stream or lake is established, it would seem in all cases to carry with it a right to the opposite bank as accessory to the use of the stream, and perhaps it even gives a right to a sufficient margin for defensive or revenue purposes, when the title is derived from occupation, or from a treaty of which the object is to mark out a political frontier “(5 ed., 123, quoted in Moore, Dig., I, 617, note.)

¹⁴ See, for example, Article III of the treaty between the United States and Spain of February 22, 1819, relative to the boundary along the river Sabine, Malloy’s Treaties, II, 1652; also texts of boundary conventions in the Argument of the United States in the Chamiza! Arbitration, 21-24.

In the Argument of the United States in the Chamizal Arbitration there is noted (p. 24) a small group of European boundary treaties, which provide that the thalweg shall be designated at fixed points, which shall thereafter be regarded as forming a fixed Une of demarcation, notwithstanding subsequent changes of the channel. The text of the boundary convention between Russia and Westphalia of May 14, 1811 (N. R. I., 382), is quoted.

¹⁵ See, for example, Articles II, III and IV of the treaty between the United States and Great Britain respecting the boundary waters between the United States and Canada of Jan. 11, 1909, Treaty Series, No. 548, Supplement to this Journal, IV, 239; also Article III of the boundary convention between the United States and Mexico of Nov. 12, 1884; Malloy’s Treaties, I, 1159; Article III of convention of limits between France and Prussia of Oct. 23, 1829, Brit. & For. St. Pap., XVI, 907.

¹⁶ See Chitty’s ed., § 271, p. 122. See also Bluntschli, Das Moderne Völkerrecht der Civuisirien Staaten, § 299; Calvo, 5 ed., I, § 342, p. 466.

¹⁷ See Norton v. Whiteside, 188 Fed. R. 356, 359.

¹⁸ See Hall, 6 ed., 123; Oppenheim, I, 254.

¹⁹ Such is the common provision of boundary conventions that refer to the matter. See, for example, Article IV of the convention between the Argentine Republic and Brazil of October 6, 1898, Brit. A For. St. P., XC, 86. See, also, Rivier I, 168.

²⁰ See Blatchford, J., in St. Louis v. Rutz, 138 U. S. 226, 249.

²¹ See, for example, definitive treaty of peace between the Allies and France of May 30, 1814, Brit. & For. St. Pap., I, pt. 1,156; also statement of E. Nys, concerning the treaties 1801-1840, affecting islands in the Rhine, in his Droit International, 2 ed., I, 430-435; also St. Louis v. Rutz, 138 U. S. 226, 250.

²² This principle is well expressed by Fiore (French translation by Antoine), II, § 781 and note. Compare, Rivier I, 168.

²³ See Treaty of Lunevffle of Feb. 9, 1801, between France and the Empire, De Clercq, Traités, I, 425; treaty between Baden and Argovie of Sept. 17, 1808, N. R., I,140; Article III of Treaty of Peace of Paris, Nov. 20, 1815, III, Brit. & For. St. P., 280, 285; decree promulgating treaty of limits between France and Spain of Dec. 2, 1856, Brit. & For. St. P., XLVII, 765; Final Act of delimitation of boundary respecting Sardinia, Austria and France, of Nov. 10, 1859, Brit. & For. St. P., LIII, 943; Declaration of Jan. 26, 1861, respecting the limit of sovereignty over bridges of the Rhine between France and Baden, De Clercq, Traités, VIII, 160; Final Act of delimitation of boundary between Austria and Italy of Dec. 22, 1867, Brit. & For. St. P., LXIII, 840; Final Act of the Powers fixing the Turko-Greek frontier, of Nov. 27, 1881, Brit. & For. St. P., LXXII, 738.

See, also, E. Nys, Le Droit International, 2 ed., I, 437; Rivier, I, 168; Oppenheim, I, § 199, note 4; G. Ullmann, Völkerrecht, 2 ed., § 80.

²⁴ Thus, in the Declaration of Jan. 21, 1861, respecting the limit of sovereignty over bridges of the Rhine between France and Baden, it is declared:

“1. The middle of the fixed bridge over the Rhine between Strasbourg and Kehl shall be regarded as the limit of sovereignty between France and the Grand Duchy of Baden.

“2. The same principle shall be adopted, hereafter, respecting the bridge of boats between Strasbourg and Kehl, as well as for all the bridges which shall be constructed in the future between France and the Grand Duchy of Baden.

“3. These provisions are independent of the limit of the waters, and shall be without prejudice as to that limit, such as is established annually, according to the thalweg of the Rhine.” (De Clercq, Traités, VIII, 160.)

²⁵ Such was the policy of the United States and Mexico, expressed in the boundary convention of Nov. 12, 1884, respecting the Rio Grande and the Rio Colorado, according to Article IV of which it is provided that: “If any international bridge have been or shall be built across either of the rivers named, the point on such bridge exactly over the middle of the main channel as herein detennined shall be marked by a suitable monument, which shall denote the dividing line for all the purposes of such bridge, notwithstanding any change in the channel which may thereafter supervene. But any rights other than in the bridge itself and in the ground on which it is built shall in event of any such subsequent change be determined in accordance with the general provisions of this convention.” (Malloy’s Treaties, I, 1159, 1160.)