In those days the valley was a complete basin, with no outlet--at least not one worth mentioning; and the heavy tropical rains and the melted snow from the mountains, poured vast quantities of water into it.

Had the valley been at the level of the sea, it would simply have become a great lake, surrounded by hills; but at three thousand feet higher, the atmosphere is rarefied, and evaporation goes on with such rapidity as to keep the accumulation of water in check.

So the affair had adjusted itself in this wise, that the land and the five lakes should divide the valley about equally between them.

It became necessary to alter this state of things, and a passage was cut at a place where the hills were but little above the level of the highest lake.

The history of this passage, the famous "Desague de Huehuetoca," is instructive enough, but it has been written so threadbare that I cannot touch it.