Some of it is stopped on its way down from the higher ground, by the evaporation of the water that was carrying it; and some is left by the lake itself, in its frequent floodings of the ground in its neighbourhood.

So small is the difference of level between the lake and the plain that surrounds it, that the slightest rise in the height of the water makes an immense difference in the size of the lake; and even a strong wind will drive the water over great tracts of ground, from which it retires when the gale ceases.

It must have been this, or something similar, that set Cortes upon writing home to Spain that the lakes were like inland seas, and even had tides like the ocean.

Of course, this impregnation with salts is ruinous to the soil, which will produce nothing in such places but tufts of coarse grass; and the shores of the lake are the most dismal districts one can imagine.

All the lakes, however, are not so salt as Tezcuco; Chalco, for instance, is a fresh-water lake, and there the fertility of the shores is very great, as I have already had occasion to notice.
As soon as the novelty of this kind of travelling had worn off, we began to find it dull, and retired under our awning to breakfast and bitter beer; which latter luxury, thanks to a suitable climate and an English brewer, is very well understood in Mexico, and is even accepted as a great institution by the Mexicans themselves.
We were just getting into a drowsy state, when an unusual bustle among the crew brought us out of our den, and we found that three hours of assiduous poling had taken us half-way across the lake, just six miles--a good test of the value of the Aztec system of navigation.