In his role as a promoter of scientific exploration of North America, Thomas Jefferson shared with Jedidiah Morse, considered by many to be the father of American geography, the patriotic desire to counteract misinformation furnished by “imperfect and erroneous sketches” describing the continent's geography by European writers. Yet his interest in the science of geography was also motivated by a concern with America's self-image in the realm of international politics, learning, and commerce. In the summer of 1802 Jefferson was prompted to send an exploring party to North America's westernmost territories in response to reading Voyages from Montreal, Alexander Mackenzie's account of his voyages across the continent to its northwest coast. At the end of his narrative, the Scottish explorer had encouraged Britain's control of a region that, if certain natural obstacles were overcome, might supply fur and fish to “the markets of the four quarters of the globe,” and proposed a line of fortified posts to be established to maintain the British Empire's presence from Lake Winnipeg to the Pacific. Jefferson understood that such action would obstruct America's westward expansion, block Russian advances from Alaska, and thus make possible a British dominion linking two great oceans. Edward Thornton, the British minister to the United States, would later observe that Mackenzie's discoveries had provoked the American President, who in 1803 was also the president of the American Philosophical Society, to concretize his dream “to set on foot an expedition entirely of a scientific nature for exploring the Western continent of America,” and that he was, furthermore, “ambitious in his character of a man of letters and science, of distinguishing his Presidency by a discovery” of a route to the Pacific Ocean by way of the Missouri, “now the only one left to his enterprise, the Northern Communication having been so ably explored and ascertained by Sir Alexander Mackenzie's journeys.