Three themes dominated the science of this period: exploration, classification, and utilization. Jefferson, in his famous letter of instruction to Meriwether Lewis, illustrated the tone: “The object of your mission is to explore the Missouri river, & such principal stream of it, as, by it's course & communication with the waters of the Pacific Ocean, whether the Columbia, Oregon, Colorado or any other river, may offer the most direct and practicable water communication across this continent, for the purposes of commerce.” He also listed among the “objects worthy of notice” animals, plants, minerals, soil, topography, and climate. Embedded in this letter – the main focus of which was trade, commerce, and navigation – were Jefferson's own scientific interests, kept subordinate because of the reluctance of Jefferson's largely mercantile oriented congress to pay for science that did not promise a commercial payoff. The pro-British mercantile elite found many of the enlightenment tendencies of the Francophile Jefferson suspect, superfluous, ungodly, but this judgment was more a matter of politics, balance, economy, and utility than any true anti-science bias. The outstanding American scientists of the previous century, Franklin, Bartram, Rittenhouse, all had roots in the mercantile class and were themselves mindful of the young country's need for practical and useful knowledge. Jefferson too thought of science in terms of utility, for though he might not view commerce as the sole guide for scientific activity, he always tended toward a measure of utility.