Monte Alegre lies on a side arm of the Amazons, a little off from its main course. This side arm, called the Rio Gurupatuba, is simply a channel running parallel with the Amazons, and cutting through from a higher to a lower point. Its dimensions are, however, greatly exaggerated in all the maps thus far published, where it is usually made to appear as a considerable northern tributary of the Amazons. The town stands on an elevated terrace, separated from the main stream by the Rio Gurupatuba, and by an extensive flat, consisting of numerous lakes divided from each other by low alluvial land, and mostly connected by narrow channels. To the west of the town, this terrace sinks abruptly to a wide sandy plain called the Campos, covered with a low forest growth, and bordered on its farther limit by the picturesque serra of Errere. The form of this mountain is so abrupt, its rise from the plain so bold and sudden, that it seems more than twice its real height. Judging by the eye, and comparing it with the mountains I had last seen,--the Corcovado, the Gavia and Tijuca range in the neighborhood of Rio,--I had supposed it to be three or four thousand feet high, and was greatly astonished when our barometric observations showed it to be somewhat less than nine hundred feet in its most elevated point. This, however, agrees with Martins's measurement of the Almeirim hills, which he says are eight hundred feet in height. Major Coutinho and I reached the serra by different roads; he crossing the Campos on horseback with Captain Faria, the commander of our steamer, and one or two other friends from Monte Alegre, who joined our party, while I went by canoe. The canoe journey is somewhat longer. A two hours' ride across the Campos brings you to the foot of the mountain, whereas the trip by boat takes more than twice that time. But I preferred going by water, as it gave me an opportunity of seeing the vast variety of animals haunting the river-banks and lakes. As this was almost the only occasion in all my journey when I passed a day in the pure enjoyment of nature, without the labor of collecting,--which in this hot climate, where specimens require such immediate and constant attention, is very great,--I am tempted to interrupt our geology for a moment, to give an account of it. I learned how rich a single day may be in this wonderful tropical world, if one's eyes are only open to the wealth of animal and vegetable life. Indeed, a few hours so spent in the field, in simply watching animals and plants, teaches more of the distribution of life than a month of closet study; for under such circumstances all things are seen in their true relations. Unhappily, it is not easy to present the picture as a whole, for all our written descriptions are more or less dependent on nomenclature, and the local names are hardly known out of the districts where they belong, while systematic names are familiar to few.