as to have suffered Mr. Fidler to come as low as 45 degrees along the eastern borders without touching that river:  yet the general course of Maria’s river from this place for fifty-nine miles, as far as captain Lewis ascended, was north 69 degrees west, and the south branch, or what we consider the Missouri, which captain Clarke had examined as far as forty-five miles in a straight line, ran in a course south 29 degrees west, and as far as it could be seen went considerably west of south, whence we conclude that the Missouri itself enters the Rocky mountains to the north of 45 degrees.  In writing to the president from our winter quarters, we had already taken the liberty of advancing the southern extremity of Mr. Fidler’s discoveries about a degree to the northward, and this from Indian information as to the bearing of the point at which the Missouri enters the mountain; but we think actual observation will place it one degree still further to the northward.  This information of Mr. Fidler however, incorrect as it is, affords an additional reason for not pursuing Maria’s river; for if he came as low even as 47 degrees and saw only small streams coming down from the mountains, it is to be presumed that these rivulets do not penetrate the Rocky mountains so far as to approach any navigable branch of the Columbia, and they are most probably the remote waters of some northern branch of the Missouri.  In short, being already in latitude 47 degrees 24’ we cannot reasonably hope by going farther to the northward to find between this place and the Saskashawan any stream which can, as the Indians assure us the Missouri does, possess a navigable current for some distance in the Rocky mountains:  the Indians had assured us also that the water of the Missouri was nearly transparent at the falls; this is the case with the southern branch; that the falls lay a little to the south of sunset from them; this too is in favour of the southern fork, for it bears considerably south of this place which is only a few minutes to the northward of fort Mandan; that the falls are below the Rocky mountains and near the northern termination of one range of those mountains:  now there is a ridge of mountains which appear behind the South mountains and terminates to the southwest of us, at a sufficient distance from the unbroken chain of the Rocky mountains to allow space for several falls, indeed we fear for too many of them.  If too the Indians had ever passed any stream as large as this southern fork on their way up the Missouri, they would have mentioned it; so that their silence seems to prove that this branch must be the Missouri.  The body of water also which it discharges must have been acquired from a considerable distance in the mountains, for it could not have been collected in the parched plains between the Yellowstone and the Rocky mountains, since that country could not supply nourishment for the dry channels which we passed on the south, and the travels of Mr. Fidler forbid us to believe that it could have been obtained from the mountains towards the northwest.