The sixteen years of Jefferson and Madison's rule furnished international tests of popular intelligence upon which Americans could depend. The ocean was the only open field for competition among nations. Americans enjoyed there no natural or artificial advantages over Englishmen, Frenchmen, or Spaniards; indeed, all these countries possessed navies, resources, and experience greater than were to be found in the United States. Yet the Americans developed, in the course of twenty years, a surprising degree of skill in naval affairs. The evidence of their success was to be found nowhere so complete as in the avowals of Englishmen who knew best the history of naval progress. The American invention of the fast-sailing schooner or clipper was the more remarkable because, of all American inventions, this alone sprang from direct competition with Europe. During ten centuries of struggle the nations of Europe had labored to obtain superiority over each other in ship-construction; yet Americans instantly made improvements which gave them superiority, and which Europeans were unable immediately to imitate even after seeing them. Not only were American vessels better in model, faster in sailing, easier and quicker in handling, and more economical in working than the European, but they were also better equipped. The English complained as a grievance that the Americans adopted new and unwarranted devices in naval warfare; that their vessels were heavier and better constructed, and their missiles of unusual shape and improper use. The Americans resorted to expedients that had not been tried before, and excited a mixture of irritation and respect in the English service, until "Yankee smartness" became a national misdemeanor. The English admitted themselves to be slow to change their habits, but the French were both quick and scientific; yet Americans did on the ocean what the French, under stronger inducements, failed to do. The French privateer preyed upon British commerce for twenty years without seriously injuring it; but no sooner did the American privateer sail from French ports than the rates of insurance doubled in London, and an outcry for protection arose among English shippers which the Admiralty could not calm. The British newspapers were filled with assertions that the American cruiser was the superior of any vessel of its class, and threatened to overthrow England's supremacy on the ocean.