During the early part of summer, the fording of streams which have their source in the Rocky Mountains is no safe or easy task. When the sun and the warm south winds begin to melt the immense piles of snow and ice in the mountains, the water comes tumbling down in torrents; and, having overflowed the rivers' banks, floods the adjacent country. By this means, new gullies and ravines are continually forming, which, when the melting process ceases, are converted into dry beds. With this rush of angry water, large rocks and masses of earth are swept from their natural seat, leaving a wreck behind that is fearfully grand to behold. The roaring of these torrents as they come leaping past and over every obstacle, resembles a low, rumbling thunder, which is reechoed through the deep forests and canons. Sometimes travelers are compelled to wait weeks before these rivers fall sufficiently to allow a safe transit. Heavy rains have the same effect to enlarge them; and, in one instance, a body of soldiers, while crossing the plains, were overtaken by these rains, which fell with such rapidity and in such quantity as to make the level prairies almost one sheet of water, while every ravine was converted into a river, swift and deep. To cross these, the men were obliged to use their best exertions with very poor means to guard against loss; and, even with the best care, one man was drowned, while several mules shared the same fate. In the prospective construction of bridges for highroads and railroad tracks across the continent, in certain seasons of the year, this sudden accumulation and explosion of water may cause trouble by sweeping them suddenly away.