tersect 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 Wilde, 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 the plates, for all of which I am indebted to her pencil.
With regard to the general tone of my work, which will be found to differ materially from that adopted in some recent publications, I shall make
