The discovery of the "Great West," or the valleys of the Mississippi and the Lakes, is a portion of our history hitherto very obscure. Those magnificent regions were revealed to the world through a series of daring enterprises, of which the motives and even the incidents have been but partially and superficially known. The chief actor in them wrote much, but printed nothing; and the published writings of his associates stand wofully in need of interpretation from the unpublished documents which exist, but which have not heretofore been used as material for history.