THE MISSOURI IS THE LONGEST RIVER IN THE WORLD, AND THE MISSISSIPPI IS ONLY A BRANCH OF IT. The Mississippi River joins its current with that of the Missouri about two hundred miles above the mouth of the Ohio; consequently, as we are now to allow the largest stream (the Missouri) to bear its name from its source all the way to the Gulf of Mexico, it follows that the Ohio flows into the Missouri and not into the Mississippi River. The Missouri, and NOT the Mississippi, is the main stream of what has been called the Mississippi Basin. The Missouri, when taken from its fountain-heads of the Gallatin, Madison, and Red Rock lakes, or, if we take the Jefferson Fork as the principal tributary, has a length, from its source to its union with the Mississippi, of above three thousand miles. The United States Topographical Engineers have credited it with a length of two thousand nine hundred and eight miles, when divested of some of these tributary extensions. The same good authority gives the Mississippi a length of thirteen hundred and thirty miles from its source to its junction with the Missouri. At this junction of the two rivers the Missouri has a mean discharge of one hundred and twenty thousand cubic feet of water per second, or one-seventh greater than that of the Mississippi, which has a mean discharge of one hundred and five thousand cubic feet per second. The Missouri drains five hundred and eighteen thousand square miles of territory, while the Mississippi drains only one hundred and sixty- nine thousand square miles. While the latter river has by far the greatest rainfall, the Missouri discharges the largest amount of water, and at the point of union of the two streams is from fifteen to seventeen hundred miles the longer of the two. Therefore, according to natural laws, the Missouri is the main stream, and the smaller and shorter Mississippi is only a branch of it. From the junction of the two rivers the current, increased by numerous tributaries, follows a crooked channel some thirteen hundred and fifty-five miles to the Gulf of Mexico. The Missouri, therefore, has a total length of four thousand three hundred and sixty-three miles, without counting some of its highest sources. The learned Professor A. Guyot, in a treatise on physical geography, written for "A. J. Johnson's New Illustrated Family Atlas of the World," informs us that the Amazon River, the great drainer of the eastern Andes, is three thousand five hundred and fifty miles long, and is the LONGEST RIVER IN THE WORLD.