as in my visits to the Central districts of Tlalpujahua, Temascaltepec, and Real del Monte, where I had the benefit of Mr. Beaufoy's observations in addition to my own.
The distances are estimated, in general, by the reputed number of leagues, and time, combined.
The rivers are merely laid down where they intersect the road, the course of most being little known.
The mountains are traced in a similar manner, nor is it attempted to connect the two great branches of the Sierra Madre, by filling up the intervening space, although their direction may be easily perceived.
The heights are taken from Humboldt, wherever he has given them, with the toises reduced to English feet; to which are added those of Real del Monte, the Doctor, Catorce, Zacatecas, and Bolaños, as measured by General Wavel, Captain Wild, Mr. Glennie, and Dr. Coulter.
The drawings were all taken upon the spot; many of them under circumstances, which would have discouraged most persons from making the attempt, as fatigue, and a burning sun, often combined to render it unpleasant. I mention this in justice to Mrs. Ward, whose name, in conformity to custom, appears upon
