"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.
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.
"The tide is perceptible five hundred miles from the sea; it does not carry the salt water up with it, but there is simply a rise and fall of the fresh water. So great is the volume of the Amazon where it enters the sea that ships can dip up fresh water while yet out of sight of land."
"In speaking of the tide," said the Doctor, "don't forget to mention the piroróco or 'bore' of the Amazon."
"I was just coming to it," replied the youth, "and cannot do better than quote a description by La Condamine, written more than a hundred years ago. Here it is:
"'During three days before the new and full moons, the period of the highest tides, the sea, instead of occupying six hours to reach its flood, swells to its highest limits in one or two minutes. The noise of this terrible flood is heard five or six miles, and increases as it approaches. Presently you see a liquid promontory, twelve or fifteen feet high, followed by another and another, and sometimes by a fourth. These watery mountains spread across the whole channel, and advance with a prodigious rapidity, rending and crushing everything in their way. Immense trees are instantly uprooted by it, and sometimes whole tracts of land are swept away.'"
"It must be a terrible thing for boats to encounter, especially the small ones," Fred remarked, as Frank concluded the above description.