and its tributaries. They supply the Indians with the greater part of their animal food, and are at all times more plentiful and easier to be obtained than birds or game from the forest. Mr. Wallace found 205 species in the Rio Negro alone, and as most of those which inhabit the upper part of the river are not found near its mouth, where there are many other kinds equally unknown in the clearer, darker, and probably colder waters of its higher branches, he estimates that at least 500 species exist in the Rio Negro and its tributary streams. In fact, in every small river and in different parts of the same river distinct kinds are found, so that it is impossible to estimate the number in the whole valley of the Amazons with any approach to accuracy. To describe the countless tribes of insects that swarm in the dense forests of that vast basin would be equally vain. In no country in the world is there more variety and beauty, nowhere are there species of larger size and of more brilliant colours. The great mass of the beetles are indeed inferior to those of tropical Africa, India, and Australia, but it is in the lovely butterflies that the Amazonian forests are unrivalled, whether we consider the endless variety of the species, their large size, or their gorgeous colour. South America is the richest part of the world in this group of insects, and the Amazons seems the richest part of South America. In more than one respect the Amazons reminds one of the ocean, from whose bosom its waters originally arose. Like the sea, it forms a barrier between various species of animals; for the monkeys on its northern bank are different from those of the forests on its southern side, and many an insect--nay, even many a bird--finds an impassable barrier in the enormous width of the river. Like the sea, it has a peculiar species of dolphin, and hundreds of miles up the stream, sea-mews and petrels, deceived by its grandeur, screech or shoot in arrowy flight over its fish-teeming waters. As over the ocean, or in the desert, the illusions of the mirage are also produced over the surface of the Marañon. The distant banks, not always clearly defined even in the morning, disappear wholly at noon, and the rays of the sun are then so refracted that the long rows of palms appear in an inverted position.