The houses, excepting those occupied by the richer classes, are dark, narrow, and filthy; and if this Augean stable be not cleansed from the accumulated filth of ages, ere the cholera shall visit it, thousands will be swept away. A stranger is surprised, in passing through the streets, at the immense number of shops which occupy the ground floor of nearly every house in the city; yet there are said to be but few failures among their occupants. The extravagant price charged for every article, retail, may perhaps account for this fact. One of the most celebrated objects of curiosity in Rio is the celebrated aqueduct, which is seen winding its way from the Corcovado along the base of many hills, intersecting the streets with its double arches, and passing over the roofs of houses to the various fountains, which are constantly thronged with negroes, carrying jars of water to the dwellings of their masters for culinary purposes--the kitchen being, in many cases, in the upper story, while the ground-floor is occupied for magazines or stables. At some of the fountains are stone troughs, for the use of the negro washer-women, which are constantly thronged with them, making most vociferous cries: a greater confusion of tongues could not have been heard at the dispersion of the builders at Babel; for there is a mixture of all the languages of Africa, from Senegal to Angola, and from Da Lagoa Bay to Zanzibar--with Portuguese, Spanish, French and English, and various Indian languages: making, in the sum total, an olla not to be surpassed by the Lingua Franca of the Mediterranean, or the bazars of British India. [Sidenote: RIO--SLAVERY--POPULATION.] Every kind of labour is here done by slaves; the heaviest burdens are dragged by them on ill-constructed drays over a rough pavement: some of them (principally criminals or runagates) are seen chained in various ways, and bending under the weight of packages too heavy for their strength. Slavery appears here in all its worst features and most disgusting deformities. Notwithstanding blacks may be seen at the altars, administering the rites of religion,--as commanders of companies or regiments, or as custom-house officers--yet poor friendless creatures (white and black) are seen at every step, nearly naked, covered with loathsome diseases, badly fed, having only the steps of some church-door or the pavement for their bed, or lying exposed to the intense heat of a tropical sun.