§ 200. Boundary mountains or hills are such natural elevations from the common level of the ground as separate the territories of two or more States from each other. Failing special treaty arrangements, the boundary line runs on the mountain ridge along with the watershed. But it is quite possible that boundary mountains belong wholly to one of the States which they separate.[376]
[376] See Fiore, II. No. 800.
Boundary Disputes.
§ 201. Boundary lines are, for many reasons, of such vital importance that disputes relating thereto are inevitably very frequent and have often led to war. During the nineteenth century, however, a tendency began to prevail to settle such disputes peaceably. The simplest way in which this can be done is always by a boundary treaty, provided the parties can come to terms.[377] In other cases arbitration can settle the matter, as, for instance, in the Alaska Boundary dispute between Great Britain (representing Canada) and the United States, settled in 1903. Sometimes International Commissions are specially appointed to settle the boundary lines. In this way the boundary lines between Turkey, Bulgaria, Servia, Montenegro, and Roumania were settled after the Berlin Congress of 1878. It sometimes happens that the States concerned, instead of settling the boundary line, keep a strip of land between their territories under their joint tenure and administration, so that a so-called condominium comes into existence, as in the case of Moresnet (Kelmis) on the Prusso-Belgian frontier.[378]
[377] A good example of such a boundary treaty is that between Great Britain and the United States of America respecting the demarcation of the international boundary between the United States and the Dominion of Canada, signed at Washington on April 11, 1908. See Martens, N.R.G. 3rd Ser. IV. (1911), p. 191.
[378] See above, § [171], No. 1.
Natural Boundaries sensu politico.
§ 202. Whereas the term "natural boundaries" in the theory and practice of the Law of Nations means natural signs which indicate the course of boundary lines, the same term is used politically[379] in various different meanings. Thus the French often speak of the river Rhine as their "natural" boundary, as the Italians do of the Alps. Thus, further, the zones within which the language of a nation is spoken are frequently termed that nation's "natural" boundary. Again, the line enclosing such parts of the land as afford great facilities for defence against an attack is often called the "natural" boundary of a State, whether or not these parts belong to the territory of the respective State. It is obvious that all these and other meanings of the term "natural boundaries" are of no importance to the Law of Nations, whatever value they may have politically.
[379] See Rivier, I. p. 166.