_August 14th._—We are very agreeably surprised in the climate here. I had expected from the moment of our arrival in the region of the Amazons to be gasping in a fierce, unintermitting, intolerable heat. On the contrary, the mornings are fresh; a walk or ride between six and eight o’clock is always delightful; and though during the middle of the day the heat is certainly very great, it cools off again towards four o’clock; the evenings are delightful, and the nights always comfortable. Even in the hottest part of the day the heat is not dead; there is always a breeze stirring. Mr. Agassiz returned this afternoon from his excursion in the harbor, more deeply impressed than ever with the grandeur of this entrance to the Amazons and the beauty of its many islands, “An archipelago of islands,” as he says, “in an ocean of fresh water.” He describes the mode of fishing of the Indians as curious. They row very softly up the creek, having first fastened the seine across from shore to shore at a lower point, and when they have gained a certain distance above it, they spring into the water with a great plash and rush down the creek in a line, driving the fish before them into the net. One draught alone filled the boat half full of fish. Mr. Agassiz was especially interested in seeing alive for the first time the curious fish called “Tralhote” by the Indians, and known to naturalists as the Anableps tetrophthalmus. This name, signifying “four-eyed,” is derived from the singular structure of the eye. A membranous fold enclosing the bulb of the eye stretches across the pupil, dividing the visual apparatus into an upper and lower half. No doubt this formation is intended to suit the peculiar habits of the Anableps. These fishes gather in shoals on the surface of the water, their heads resting partly above, partly below the surface, and they move by a leaping motion somewhat like that of frogs on land. Thus, half in air, half in water, they require eyes adapted for seeing in both elements, and the arrangement described above just meets this want.