[Footnote 292: The literature on aviation is abundant, see Holtzendorff, II. p. 230; Lawrence, § 73; Bonfils, Nos. 531{ 1}-531{ 9}; Despagnet, Nos. 433 _bis_ and 433 _ter_; Mérignhac, II. pp. 398-410; Nys, I. pp. 523-532; Grünwald, "Das Luftschiff, &c." (1908); Meili, "Das Luftschiff, &c." (1908); Meurer, "Luftschiffahrtsrecht" (1909); Meyer, "Die Erschliessung des Luftraums und ihre rechtlichen Folgen" (1909); Magnani, "Il diritto sullo spazio aereo e l'aeronautica" (1909); Leech, "The Jurisprudence of the Air" (1910), a reprint from the _Journal of the Royal Artillery_, vol. XXXVII.; Lycklama à Nijeholt, "Air Sovereignty" (1910); Hazeltine, "The Law of the Air" (1911); Bielenberg, "Die Freiheit des Luftraums" (1911); Catellani, "Il diritto aereo" (1911); Sperl, "Die Luftschiffahrt, &c." (1911); Loubeyre, "Les principes du droit aérien" (1911); Fauchille in Annuaire, XIX. (1902) pp. 19-114, XXIV. (1911), and in R.G. VIII. (1901), pp. 414-485, XVII. (1910), pp. 55-62; Zitelmann in the _Zeitschrift für internationales Privat- und Öffentliches Recht_, XIX. (1909), pp. 458-496; Baldwin and Kuhm in A.J. IV. (1910), pp. 95-108, 109-132; Baldwin in Z.V. V. (1911), pp. 394-399.]
[Footnote 293: The Institute of International Law is studying the question of aviation, and passed, in 1911, at its meeting in Madrid, some rules concerning the "Régime juridiques des Aéronefs"; see Annuaire, XXIV. (1911).]
Aviation through the atmosphere above the Open Sea will require special regulation on account of the dangers to the vessels of all nations traversing the sea, as will also aviation in general in time of war.
[Sidenote: Inalienability of Parts of Territory.]
§ 175. It should be mentioned that not every part of territory is alienable by the owner-State. For it is evident that the territorial waters are as much inseparable appurtenances of the land as are the territorial subsoil and atmosphere. Only pieces of land together with the appurtenant territorial waters are alienable parts of territory.[294] There is, however, one exception to this, since boundary waters[295] may wholly belong to one of the riparian States, and may therefore be transferred through cession from one to the other riparian State without the bank itself. But it is obvious that this is only an apparent, not a real, exception to the rule that territorial waters are inseparable appurtenances of the land. For boundary waters that are ceded to the other riparian State remain an appurtenance of land, although they are now an appurtenance of the one bank only.