Gage wrote one of the most important English travel books on America in the 17th century, exciting the English with envy—never a difficult thing to do in those days—on the wealth and the relative defenselessness of the Spanish in North America, laying out a concrete plan for domination of the continent. This map gives an idea of the paucity of specific European knowledge of the interior of North America and especially Louisiana on the eve of concerted effort by the French to explore and colonize the region. Yet, even here one sees the great, beckoning mystery of a central river, the unnamed Mississippi, nearly connecting with a huge outstretched arm of the St. Lawrence, nothing shown as yet of the Great Lakes or the elusive northwest of the vast continent.