Again a rush was heard, which came nearer and more near, filling us with dread, till it struck us with the suddenness of a blow. It was as though all those cones had drawn closer and closer together, till they were piled into one consolidated mountain of dust, pressed down by the mass in the air upon our heads. For a time all our efforts to see or to speak were vain. We could hardly breathe. If we moved at all, it was by setting our backs against the elements and pushing with all our strength. There was not a drop of rain; it was a storm of dust--a _sirocco_. Fortunately for us, we were near the _meson_, which we entered after being half an hour exposed to its fury, and as it was abating. Every thing was penetrated by it, and it seemed as though water could not clean our eyes or our throats. In the _mesons_, the various apartments for travelers, the stables, the eating-room, and all the offices, are built around a spacious paved court, upon which all the windows and doors open. A large gate forms the entrance, which is closed and bolted at night. The rooms for travelers, often twenty feet square, are entirely unfurnished. He is to supply his own bed and bedding, which he spreads out upon a floor which seems never to have been swept. For his meals he must go to the _fonda_, and order what he may choose or what they may have. One dish at a time is spread upon the bare table, which is often furnished with plates, but not often with knives, forks, or spoons. A variety of soups, made hot with red pepper, and a slice of bread, forms the first course. Then follows rice, with thin Indian cakes. Sometimes squash fried in lard is added. A favorite dessert is the Mexican custard, made of rice or chocolate. Coffee, wine, or _pulque_, a drink made of the maguey, closes the entertainment. There are distilleries in the country where the pulque is converted into a most hateful species of whisky. In the morning the horses and mules are led out into the court, every preparation is made, and the travelers take their leave, throwing behind them their hasty adieus. These mesons in city and country are very filthy, and much infested with vermin. In one instance we saw a number of _Tarantulas_--the venomous black spider of the tropics--hanging upon the walls of our room after we had slept upon its floor. On the 22d of March we entered San Luis Potosi. This is a large city, possessing considerable wealth. It is near the silver mines, and contains a mint. We saw here, for the first time, a stage-coach. It was up for the city of Mexico, distant about three hundred miles, which journey is accomplished in six days, at an expense of $25 for a seat. The coach consists of a large unwieldy frame, upon which is swung the body, which is comparatively small.