Entering the Amazon from the Madeira, the steamer turned her prow to the westward and ascended the great river for sixty miles, to the mouth of the Rio Negro. The yellow waters of the Amazon and Madeira had reminded Frank and Fred of the Mississippi; there was some dispute between them as to which of the two streams was dirtier in color, but they finally agreed that the Madeira was the worse of the two. "We will compare the Madeira to the Missouri," said Fred, "and the united stream to the Mississippi as we see it below the mouth of the Ohio." Frank agreed to this distinction, and there the discussion ended. The Amazon brings down a vast amount of alluvial matter which it receives from its tributaries, in addition to what it breaks away from the banks on its own account below the mouth of the Madeira. The sediment is carried far into the sea, and there is no proper delta at its mouth, as with the other great rivers of the world. Frank made some notes concerning the great river, which we will now introduce. "The Amazon," said he, "is undoubtedly the largest river on the globe, but it is not the longest. Lieutenant Herndon estimates its length, considering the Huallaga as the head-stream, at three thousand nine hundred and forty-four miles; another authority makes it three thousand miles; another two thousand seven hundred and fifty, and other travellers give various figures up to three thousand six hundred miles. The differences arise from disputes as to which of the tributaries should be called the head-stream. "The Amazon is rather a vast system of rivers than a river by itself. More than three hundred and fifty branches and tributaries unite to form the Amazon; all the rivers flowing from the eastern slope of the Andes from three degrees north latitude to nineteen degrees south latitude, a distance of two thousand miles, as we follow the windings of the mountain chain, pour into the Amazon and contribute to its immense volume. It is three hundred and twelve feet deep at its mouth, and where it crosses the Brazilian frontier at Tabatinga it is sixty-six feet deep! The _Great Eastern_ steamship might navigate it for more than a thousand miles from the sea. [Illustration: NATIVES ON THE MIDDLE AMAZON.] "Half a million cubic feet of water flow out of the Amazon every second, or thirty million cubic feet in a minute. The ordinary current is three miles an hour. Two thousand three hundred miles from the sea it is three fourths of a mile wide, at the mouth of the Madeira it is three miles wide, and below Santarem it is ten miles from side to side. Its mouth is said to be one hundred and eighty miles wide, but this is hardly a fair statement of the case, as the island of Marajo occupies a large portion of the mouth, and the river reaches the ocean through many channels.