Before us the valley wound between partly wooded low hills, behind which the higher base now rose. For several days we marched along this valley, till on one afternoon we looked down from a hill on the blue crystalline waters of the southern Platte, which coming down from the Medicine hills, rustled through the valley at our feet. The river was large even here, and shot with the speed that characterizes the streams in this country, and with many windings between its wood-clad banks. Before us, where the river described a sharp curve, the banks were stony on both sides, and seemed from time immemorial to have been used by the inhabitants of these countries as a ford. At this moment, when probably for the first time the eyes of white men rested on this ford, a countless herd of buffaloes was occupied in crossing. They were coming southward from the mountains, and pressed shoulder to shoulder in dense masses to water in the river, while others came down the hills in a black line. The roars of these thirsty wanderers filled the air and rang through the hills in a thousand echoes. They dashed by hundreds impetuously from the high bank into the deep, rapid stream, on either side of the ford, and drifted with it into the dark overarching wood. We stopped for a long time gazing down at this scene and awaiting the end of the herd, whose head had disappeared some time previously in the valley on our left, while dense masses still continued to pour down without a check from the hills to the water. At length, at the end of an hour, only a few laggards came, after at least five thousand buffaloes had crossed the river, and yet the number of these animals is said to be quite insignificant compared with what it was twenty years ago. Who knows whether fifty years hence they will exist anywhere but in natural history? We were obliged to let the wanderers pass, as we also wanted to cross the river, though in the opposite direction, and we should have run a risk of the whole herd marching over us, had we got in their way. We now rode down into the river; but, although so great a number of huge animals had passed through it, the water was as clear and bright as if a stone had never been stirred on its bottom. We watered our cattle, and followed the path by which the buffaloes had found their way to this ford, on the supposition that they had rendered it quite passable, and that they had come from the southern prairies to which we were bound. [Illustration: BUFFALOES CROSSING A RIVER. _p. 333._]