The houses of Mexico, some of which are very spacious and magnificent, are constructed generally of a light volcanic production called _tetzontli_, in some instances cut smooth and square, but more frequently rough, when the walls are plastered with lime and painted. The handsomest are built of light gray porphyry. They are mostly of two stories, some of three, with _axoteas_ or flat roofs. They have all open squares. A gate, large enough for carriages to pass through, leads from the street into the _patio_, or court yard. The basement upon the street is occupied commonly as a store or shop, and in the rear are the stables. Across the patio, fronting the gate, is the staircase, which leads to the _corridors_, or interior porticoes, which surround the area, and are ornamented with flowers. From the corridors, the doors open into the various rooms, which communicate with each other around the whole area, in instances where the house is so large as to occupy the four sides. It is an airy style of building, the windows being large, level with the brick floor, opening like double doors, and is well adapted to the delightful climate of Mexico. The most serious evil is the want of privacy to the chambers. Each window has its balcony. The streets of Mexico run nearly from north to south, and from east to west, crossing at right angles. The greatest longitudinal length is about two miles--the latitudinal about a mile and three quarters;[2] but as the figure of the city is unequal, these lengths are far from uniform. In either direction the view is terminated by the mountains which bound the plain of Mexico. In the central and most frequented parts of the city, the streets are well paved and are kept clean; but apart from these, they are amazingly dirty--the drains passing through the centre being open, offensive both to the sight and to the smell. [Footnote 2: This measure does not mean the distance of the opposite _garitas_ or custom-house gates from each other, which is considerably greater--but comprises the compactly built part of the city, not comprehending the scattered houses in the outskirts.]