generations. Now, when the trees were cut down, the small plants which grew in their shade died too, and left the bare earth to serve as a kind of natural evaporating apparatus. And, between these two causes, it has come to pass that the extent of the lakes has been so much reduced, and that Mexico stands on the dry land—if, indeed, that may be called dry land, where you cannot dig a foot without coming to water.
During the Tertiary period the whole valley of Mexico was one great lake. Whether the proportion of water to land had adjusted itself before the country was inhabited, or whether during historical times the lakes were still gradually diminishing by the excess of evaporation over the quantity of water supplied by rain and snow, is an open question. At any rate the two causes I have mentioned will account for the changes which have taken place since the conquest.
Taking it as a whole, Mexico is a grand city, and, as Cortes truly said, its situation is marvellous. But as for the buildings, I should be sorry to