the Trombetas, a large river flowing through the interior of Guiana. Hills and lowlands alike are covered with a sombre rolling forest. The river here is contracted to a breadth of rather less than a mile (1738 yards), and the entire volume of its waters, the collective product of a score of mighty streams, is poured through the strait with tremendous velocity.[1] It must be remarked, however, that the river valley itself is not contracted to this breadth, the opposite shore not being continental land, but a low alluvial tract, subject to inundation more or less in the rainy season. Behind it lies an extensive lake, called the Lago Grande da Villa Franca, which communicates with the Amazons, both above and below Obydos, and has therefore the appearance of a by-water or an old channel of the river. This lake is about thirty-five miles in length, and from four to ten in width; but its waters are of little depth, and in the dry season its dimensions are much lessened. It has no perceptible current, and does not therefore now divert any portion of the waters of the Amazons from their main course past Obydos.
I remained at Obydos from the 11th of October to the 19th of November. I spent three weeks here, also,
- ↑ It was formerly believed that the river at the strait of Obydos could not be sounded on account of its great depth and the velocity of the current. Lieut. Herndon, of the United States navy, succeeded in doing so, however, in 1852. He found a depth of 30 to 35 fathoms, but in one place he thought he had not touched the bottom at 40 fathoms. Von Martius, estimating the depth in the middle at 60 fathoms, and on the side at 20, and the velocity of the current at 2.4 feet per second, estimated that 499,584 cubic feet of water passed through the strait in each second of time. The tides are felt here in the dry season, but the flood does not press back the current of the Amazons.
