Sunday, 26th, proceeded on at an early hour by means of the towline, using our oars merely in passing the river, to take advantage of the best banks.  There are now scarcely any low grounds on the river, the hills being high and in many places pressing on both sides to the verge of the water.  The black rock has given place to a very soft sandstone, which seems to be washed away fast by the river, and being thrown into the river renders its navigation more difficult than it was yesterday:  above this sandstone, and towards the summits of the hills, a hard freestone of a yellowish brown colour shows itself in several stratas of unequal thickness, frequently overlaid or incrusted by a thin stratum of limestone, which seems to be formed of concreted shells.  At eight and a quarter miles we came to the mouth of a creek on the north, thirty yards wide, with some running water and a rocky bed:  we called it Windsor creek, after one of the party.  Four and three quarter miles beyond this we came to another creek in a bend to the north, which is twenty yards wide, with a handsome little stream of water:  there is however no timber on either side of the river, except a few pines on the hills.  Here we saw for the first time since we left the Mandans several soft shelled turtles, though this may be owing rather to the season of the year than to any scarcity of the animal.  It was here that after ascending the highest summits of the hills on the north side of the river, that captain Lewis first caught a distant view of the Rock mountains, the object of all our hopes, and the reward of all our ambition.  On both sides of the river and at no great distance from it, the mountains followed its course:  above these, at the distance of fifty miles from us, an irregular range of mountains spread themselves from west to northwest from his position.  To the north of these a few elevated points, the most remarkable of which bore north 65 degrees west, appeared above the horizon, and as the sun shone on the snows of their summits he obtained a clear and satisfactory view of those mountains which close on the Missouri the passage to the Pacific.  Four and a half miles beyond this creek we came to the upper point of a small sand island.  At the distance of five miles between high bluffs, we passed a very difficult rapid, reaching quite across the river, where the water is deep, the channel narrow, and gravel obstructing it on each side:  we had great difficulty in ascending it, although we used both the rope and the pole, and doubled the crews:  this is the most considerable rapid on the Missouri, and in fact the only place where there is a sudden descent:  as we were labouring over them, a female elk with its fawn swam down through the waves, which ran very high, and obtained for the place the name of the Elk Rapids.  Just above them is a small low ground of cottonwood trees, where, at twenty-two and a quarter miles we fixed our encampment, and were joined by captain Lewis, who had been on the hills during the afternoon.