SIR: Agreeably to your appointment as a member of the expedition to explore the sources of the Mississippi, by the way of the Lakes, I proceeded to join the party organized for that purpose at Detroit, by His Excellency Lewis Cass. Diurnal notes were kept of the changes in the geological features of the regions visited; of the mineralogy of the country; and of such facts as could be ascertained, with the means at command, to determine its general physical character and value.[209] [209] The two geological profiles of the Mississippi Valley and the Lake Basins accompanying the original are here omitted; as, also, most of the illustrative views of scenery which accompanied the original. I have heretofore reported to you the facts and appearances which indicate the existence of the ores of copper, and of valuable deposits of copper in its native form, in the basin of Lake Superior--a point which constituted one of the primary objects to which my attention was called--and I now proceed to state such particulars in the topics confided to me as fell within my observation. In generalizing the facts, it must be observed that the expedition had objects of a practical character relative to the number, disposition, and feelings to be learned respecting the Indian tribes; that the transit over large portions of the country was necessarily rapid; and that few opportunities of elaborate or long-continued observations occurred at any one point. The topography was committed to a gentleman who is every way qualified for that topic, who was well supplied with instruments, and who will do ample justice to that department. I make these remarks to prepare you for a class of observations which are necessarily technical, and quite imperfect, and to which it is felt that it will not be an easy task to impart a high degree of interest, whatever may have been the anticipations.