HYPSOMETRIC ADDENDA. 285 



Norte; one from Chihuahua to Reynosa by Parras; and 

 one from Fort Independence (a little to the east of the 

 Confluence of the Missouri and the Kanzas River) to Santa 

 3?e. The calculation is founded on daily corresponding 

 observations of the barometer, made by Engelmann at St. 

 Louis, and by Lilly at New Orleans. If we consider that 

 the difference of latitude between Santa Ee and Mexico is 

 16, and that thus (apart from deviations from a straight 

 line) the distance in the north and south direction is above 

 960 geographical miles, we are led to inquire whether there 

 be in any other part of the whole globe a similar conforma- 

 tion of the Earth, equal in extent and elevation (between 

 5000 and 7000 French, or 5330 and 7460 English feet 

 above the level of the sea) to the highland of which I have just 

 given the levelling, and yet over which four-wheeled waggons 

 can travel as they do from Mexico to Santa Ee. It is 

 formed by the broad, undulating, flattened crest of the 

 chain of the Mexican Andes, and is not the swelling of a 

 valley between two mountain chains, as is the case in some 

 other remarkable elevations of plain or undulating suface 

 in the Northern Hemisphere, in the "Great Basin" between 

 the Rocky Mountains and the Sierra Nevada of California, 

 in the Southern Hemisphere, in the high plain of the lake 

 of Titicaca, between the eastern and western chains of the 

 Andes of Bolivia, and in Asia, in the highlands of Thibet, 

 between the Himalaya and the Kuen-ltin. 



