§ 189. Instances have occurred when enemy vessels which were forced by stress of weather to seek refuge in a belligerent's harbour were granted exemption from seizure.[376] Thus, when in 1746, during war with Spain, the _Elisabeth_, a British man-of-war, was forced to take refuge in the port of Havanna, she was not seized, but was offered facility for repairing damages, and furnished with a safe-conduct as far as the Bermudas. Thus, further, when in 1799, during war with France, the _Diana_, a Prussian merchantman, was forced to take refuge in the port of Dunkirk and seized, she was restored by the French Prize Court. But these and other cases have not created any rule of International Law whereby immunity from attack and seizure is granted to vessels in distress, and no such rule is likely to grow up, especially not as regards men-of-war and such merchantmen as are easily convertible into cruisers. [Footnote 376: See Ortolan, II. pp. 286-291; Kleen, II. § 210, pp. 492-494.] [Sidenote: Immunity of Hospital and Cartel Ships.] § 190. According to the Hague Convention, which adapted the principles of the Geneva Convention to warfare on sea, hospital ships are inviolable, and therefore may be neither attacked nor seized; see below in §§ 204-209. Concerning the immunity of cartel ships, see below in § 225. [Sidenote: Immunity of Mail-boats and of Mail-bags.] § 191. No general rule of International Law exists granting enemy mail-boats immunity from attack and seizure, but the several States have frequently stipulated such immunity in the case of war by special treaties.[377] Thus, for instance, Great Britain and France by article 9 of the Postal Convention of August 30, 1860, and Great Britain and Holland by article 7 of the Postal Convention of October 14, 1843, stipulated that all mail-boats navigating between the countries of the parties shall continue to navigate in time of war between these countries without impediment or molestation until special notice be given by either party that the service is to be discontinued. [Footnote 377: See Kleen, II. § 210, pp. 505-507.] Whereas there is no general rule granting immunity from capture to enemy mail-boats, enemy _mail-bags_ do, according to article 1 of Convention XI., enjoy the privilege of such immunity, for it is there enacted that the postal correspondence of neutrals or belligerents, whether official or private in character, which may be found on board a neutral[378] or enemy ship at sea, is inviolable, and that, in case the ship is detained, the correspondence is to be forwarded by the captor with the least possible delay. There is only one exception to this rule of article 1, for correspondence destined to or proceeding from a blockaded port does not enjoy the privilege of immunity. [Footnote 378: See below, §§ 319 and 411.] It must be specially observed that postal correspondence, and not parcels sent by parcel post, are immune from capture. III