At the request of the latter he drew up a memoir on the reorganization of the western mines, which was well received.
Some legislation appeared necessary.

Meantime Mr.Calhoun, who was struck by the earnestness of his views and scientific enterprise, offered him the situation of geologist and mineralogist to an exploring expedition, which the war department was about dispatching from Detroit to the sources of the Mississippi under the orders of Gen.

Cass.
This he immediately accepted, and, after spending a few weeks at the capital, returned in Feb., 1820, to New York, to await the opening of the interior navigation.

As soon as the lakes opened he proceeded to Detroit, and in the course of two or three weeks embarked on this celebrated tour of exploration.

The great lake basins were visited and explored, the reported copper mines on Lake Superior examined, and the Upper Mississippi entered at Sandy Lake, and, after tracing it in its remote mazes to the highest practical point, he descended its channel by St.Anthony's Falls to Prairie du Chien and the Du Buque lead mines.