STRAITS OF OBYDOS 



159 



of sand, in some places several feet thick, and the whole 

 formation rests on strata of sandstone, which are exposed 

 only when the river reaches its lowest level. Behind the 

 town rises a fine rounded hill, and a range of similar ele- 

 vations extends six miles westward, terminating at the 

 mouth of 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 though 

 the strait with tremendous velocity^. It must be re- 

 marked, however, that the river valley itself is not con- 

 tracted 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 appear- 

 ance 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 

 h.as 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 1 1 th of October to the 

 19th of November. I spent three weeks here, also, in 

 1859, when the place was much changed through the 

 influx of Portuguese immigrants and the building of a 

 fortress on the top of the bluff. It is one of the pleasantest 



^ 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. 



