tution of New Spain than the reunion of my two sections, No. vII and VIII. A simple consideration of the true direction of the Cordillera of Anahuac is sufficient to prove what I advance. The central chain of the mountains runs from the province of Oaxaca to that of Durango, from the S.E. to the N.W.; consequently, the plane of projection, to be perpendicular to the longitudinal axis of the Cordillera, should not be placed parallel to the equator, but drawn from the N.E. to the S. W. By reflecting on the particular structure and limits of the group of mountains, in the neighbourhood of the capital of Mexico, we shall find that the reunion of the two sections, No, vII and vIII, gives a less imperfect representation ofthe conformation of the country than we should be tempted to believe from purely theoretical ideas. In this mountainous region, between the 19° and 20° of latitude, nothing announced a longitudinal crest. There are none of those parallel chains which geologists always admit in their works, and which geographers represent in the most arbitrary manner, in their maps of the two continents, like ranges of elevated dikes.

The Cordillera of Anahuac increases towards the north, from whence the inclined planes formed by the eastern and western declivities are not parallel to one another in their middle direction. This direction is almost N. and S. along the coast of the gulf of Mexico, while it is S.E. and N.W.

in the declivity opposite the Great Ocean. Hence the sections, to be perpendicular to the lines of declivity, cannot be in the same plane of projection.

VIII. PHYSICAL VIEW OF THE CENTRAL TABLE-LAND OF NEW SPAIN,

The section of the road leading from Mexico to the mines of Guanaxuato, the richest of the known world, was drawn up under my eye at Mexico, by M. Raphaël Davalos *, a pupil of the school of mines, and a very zealous young man, This drawing displays to the naturalist the great elevation of the table-land of Anahuac, which extends to the north much beyond the torrid zone. The extraordinary configuration of the Mexican soil recalls the elevated plains of central Asia. It would be interesting to continue my section from Guanaxuato to Durango and Chihuahua, particu larly to Santa Fe in New Mexico. For the tableland of Anahuac, as we shall hereafter prove †, preserves towards the north for an extent of more

* M. Davalos, as well as M. Juan Jose Rodriguez, a native of the Parral, in the provincias internas, and well informed in physical science, were so good as to assist me for several months in the construction of a great number of geological maps which will be afterwards published. I am pleased to have an opportunity of giving a public testimony of my gratitude to gentlemen so distinguished for their talents and application. Book I. and book III.

than two hundred leagues more than 2000*, and for an extent of five hundred leagues more than 800 metres of absolute elevation.

IX. PICTURESQUE VIEW OF THE VOLCANOS OF MEXICO OR LA PUEBLA.

This plate and the immediately following one were destined at first to appear in the physical atlas, which will accompany the historical account of my travels in the equinoxial regions. I mean to unite in that atlas such sketches as will show the physiognomy of the colossal summits which crown the ridge of the Cordilleras, and form as it were their crest. I thought that these contours, compared with those in the excellent itinerary of M. Ebel, or the beautiful drawings of M. Osterwald, might prove interesting to the geologists who wish to study comparatively the Alps of Switzerland, and the Andes of Mexico and Peru. Though the object of the work which I now publish is more to describe the territorial riches than the geological constitution of New Spain, I have thought proper to add to the Mexican atlas the picturesque views No. Ix and x, to serve as a supplement to the map of the valley (Plate III.), and to give a more lively idea of the beauty of the situation of the city of Mexico. These same summits, the Popocatepetl and the Citlaltepetl, the first of which is

* 6560 feet. Trans.

+ 2624 feet. Trans.