fluences contingent on its great altitude. The sanitary conditions of the two chief commercial centers of the republic, namely, the city of Mexico and of Vera Cruz, are, however, so extraordinary and so obstructive to national progress that any review of the country would be imperfect that neglected to notice them. The evil in the case of the former is local and not climatic, and is due to the circumstance that the site of the city is "a bowl in the mountains," so that drainage from it is now, and always has been, very difficult. And, as years have passed, and the population living within the bowl has multiplied, the evil has continually increased, until Lake Tezcoco, which borders the city, and on which Cortes built and floated war-galleys, has been nearly filled up with drainage deposits which have been carried into, it through an elaborate system of city sewers. If these sewers ever had fall enough to drain them, they have, as the result of the filling up of this lake, little or none now, and the result is that they have become in effect an immense system of cess-pools; while the soil, on which from 250,000 to 300,000 people live, has become permeated with stagnant water and filth inexpressible. And were it not for the extreme dryness and rarefaction of the air, which, as before pointed out, prevent the putrefaction of animal substances,
