The navigation upon this river is very great. Ships seldom ascend higher than Natchez. It is navigable for boats of the largest size as far as the Ohio. The number of steam-boats upon the Mississippi is about three hundred. Their size is from five hundred and forty tons downwards. The passage from Cincinnati to New Orleans and back has been made in nineteen days. From New Orleans to Louisville the shortest passage has been eight days and two hours, the distance being one thousand six hundred and fifty miles, and against the current. The steam-boats have generally high-pressure power, and many fatal explosions have happened upon these waters. The first steam-vessel here was built in 1810.[5] The _Missouri_ rises in the Rocky Mountains in nearly the same parallel with the Mississippi, and about a mile distant from the head-waters of the Columbia. The most authentic information we have yet had of the sources of this mighty river is from its first intrepid American discoverers, Lewis and Clarke. What may properly be called the Missouri, seems to be formed by three considerable branches, which unite not far from the bases of the principal ranges of the mountains. To the northern they gave the name of Jefferson, to the middle Gallatin, and to the southern Madison. All these streams run with great velocity, throwing out large volumes of water; their beds are formed of smooth pebble and gravel, and their waters are perfectly transparent. One hundred and a half miles beyond the forks of the Missouri are the forks of Jefferson river; two subordinate branches of which are called Wisdom and Philanthropy, one coming from the north-west, and the former from the south-east. Wisdom river is fifty yards wide, cold, rapid, and containing a third more water than the Jefferson; it seems to be the drain of the melting snows on the mountains, but is unnavigable on account of its rapidity. One hundred and forty-eight miles farther up is the extreme navigable point of the river in north latitude forty-three degrees thirty minutes and forty-three seconds. Two miles beyond this is a small gap or narrow entrance, formed by the high mountains which recede on each side, at the head of an elevated valley, ten miles long and five broad, so as to form a beautiful cove several miles in diameter. From the foot of one of the lowest of these mountains, which rises with a gentle ascent of half a mile, issues the remotest water of the Mississippi. At the source, we are told that the weather is so cold at the end of August, that water standing in vessels exposed in the night air has been frozen to the depth of a quarter of an inch.