The evil schemes of Spain did not stop, however, with the enactment of laws, or their administration. The precious metals had originally tempted her, as we have already seen, and she did not fail to build up a commercial system which was at once to bind the colonists forever to the mines, whilst it enriched and excited her industry at home in arts, manufactures, agriculture, and navigation. As the Atlantic rolled between the old world and the new, America was excluded from all easy or direct means of intercourse with other states of Europe, especially at a period when the naval power of Spain was important, and frequent wars made the navigation of foreign merchantmen or smugglers somewhat dangerous in the face of her cruisers. Spain therefore interdicted all commercial intercourse between her colonies and the rest of the world, thus maintaining a strict monopoly of trade in her own hands. All imports and exports were conveyed in Spanish bottoms, nor was any vessel permitted to sail for Vera Cruz or Porto Bello, her only two authorized American ports, except from Seville, until the year 1720, when the trade was removed to Cadiz as a more convenient outlet. It was not until the War of the Succession that the trade of Peru was opened, and, even then, only to the French. By the peace of Utrecht, in 1713, Great Britain with the _asiento_, or contract for the supply of slaves, obtained a direct participation in the American trade, by virtue of a permission granted her to send a vessel of five hundred tons annually to the fair at Porto Bello. This privilege ceased with the partial hostilities in 1737, but Spain found herself compelled, on the restoration of peace in 1739, to make some provision for meeting the additional demand which the comparatively free communication with Europe had created. Licenses were granted, with this view, to vessels called register-ships, which were chartered during the intervals between the usual periods for the departure of the galeons. In 1764, a further improvement was made by the establishment of monthly packets to Havana, Porto Rico and Buenos Ayres, which were allowed to carry out half cargoes of goods. This was followed in 1774, by the removal of the interdict upon the intercourse of the colonies with each other; and, this again, in 1778, under what is termed a decree of free trade, by which seven of the principal ports of the peninsula were allowed to carry on a direct intercourse with Buenos Ayres and the South Sea.[21] Up to the period when these civilized modifications of the original interdict were made, the colonists were forbidden to trade either with foreigners or with each other's states, under any pretext whatever. The penalty of disobedience and detection was death.