And these masters of England, never interested in the colonies apart from their commercial value, were less so than ever during this Indian summer of prosperous content. Rising prices made the era of, the first Georges a golden age of agriculture; while the effect of the French wars was to "exalt beyond measure the maritime and commercial supremacy of England." The Treaty of Meuthen facilitated the importation of cloth into Portugal and the flow of Brazilian bullion to London. Levantine trade began to open to England after the conquest of Gibraltar and Minorca. English merchants acquired special privileges at Cadiz by the Treaty of Utrecht; and the _Assiento_ gave to the South Sea Company a monopoly of importing slaves into New Spain, and enabled it to secure, "by the ingenuity of British merchants," the greater part of the general commerce of the Spanish colonies. In 1710, the number of vessels clearing from English ports was 3550; it was 6614 in 1714; and during the same period the shipping of London increased from 806 to 1550. In 1758, imports from the continental colonies into England stood at L648,683, and from the West Indies at L1,834,036. "The colonies," said the elder Horace Walpole, "are the source of all our riches"; for it was the colonies, and above all the West Indies,--that subterranean channel by which the silks and teas from Vera Cruz, and Peruvian gold from Puerto Bello, found their way into England,--which alone "preserve the balance of trade in our favour."