RIO NEGRO TO BAHIA BLANCA.

July 24th, 1833.—The Beagle sailed from Maldonado, and on August the 3d she arrived off the mouth of the Rio Negro. This is the principal river on the whole line of coast between the Straits of Magellan and the Plata. It enters the sea about three hundred miles south of the estuary of the latter. About fifty years since, under the old Spanish government, a small colony was established here; and it is still the most southern position (lat. 41°) on this eastern coast of America which is inhabited by civilized man.

The country near the mouth of the river is wretched in the extreme: on the south side a long line of perpendicular cliffs commences, which exposes a section of the geological nature of the country. The strata are of sandstone, and one layer was remarkable, from being composed of a firmly-cemented conglomerate of pumice pebbles, which must have travelled more than four hundred miles, from the Andes. The surface is every where covered up by a thick bed of gravel, which extends far and wide over the open plain. Water is extremely scarce, and, where found, is almost invariably brackish. The vegetation is scanty; and although there are bushes of many kinds, all are armed with formidable thorns, which seem to warn the stranger not to enter on these inhospitable regions.