7. Another fact of great importance is the endeavour, which first manifested itself in the World Postal Union of 1874, to carry out the international administration of common interests, economic and other, by means of more or less general international unions. In this way a series of international administrative unions, often conjoined with special international boards, have been called into existence.
[Sidenote: Legislation of the Peace Conferences and of the Naval Conference of London.]
8. With the end of the nineteenth and the first decade of the twentieth century, in which occur the first and second Peace Conferences at The Hague and the Naval Conference of London, the development of international law enters upon a new and pregnant epoch. If hitherto, despite the momentous law-making treaties of the nineteenth century, international law was essentially a book-law, a system erected by greater or smaller authorities on the foundations of state practice and in its details often uncertain and contested, it is now subjected more and more, and in a wide domain, to the legislating influence of law-making international conventions. To mention only the principal matters: A code has been issued which, full of lacunae as it is, nevertheless encompasses the whole area of land war; it has been laid down that war shall only be begun by a declaration of war; the employment of force for the recovery of contract-debts has been forbidden; the rights and duties of neutrals in land war and naval war, the treatment of enemy merchant vessels at the outbreak of hostilities, and the conditions of the conversion of merchant vessels into men-of-war have been legislatively fixed; rules concerning the laying of submarine mines, concerning bombardment by naval forces in time of war, concerning the application of the principles of the Geneva Convention to naval warfare, concerning certain limitations on the right of prize in naval warfare have been agreed on; many states have concurred in a prohibition of the discharge of explosive missiles from air-ships; and a code of the rules of naval warfare, so far as it touches the trade of neutrals, dealing with the topics of blockade, contraband of war, unneutral service, destruction of neutral prizes, sale of enemy merchantmen to neutrals, enemy property, convoy and so forth, has been agreed on, though still unratified.