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theoretical ideas have never been very successful. For the true configuration of the earth is so much the more difficult to be discovered, as the pelagick currents, and thegreater number of the rivers which have changed the surface of the globe, have totally disappeared. The most perfect acquaintance with those which have existed, and those which actually exist in our days, might instruct us as to the slope of the vallies, but by no means as to the absolute height of the mountains, or the position of their chains.

I have traced on my map of New Spain the direction of the Cordilleras, not from vague suppositions or hypothetical combinations, but from a great variety of data furnished by persons who had visited the Mexican mines. The most ele. vated groupe of mountains is to be found in the environs of the capital, under the 19 of latitude. I examined myself the part of the Cordilleras of Anahuac, between the parallels of 16° 50' and 21° 0', for a breadth of more than 140 leagues. It was in this region that I made the greatest number of barometrical and geodesical measurements, of which the results served for my geological sections. The manuscript maps of M. Velasquez, and of MM. Costanzo and Pagaza, were of great use to me for the northern provinces. M. Velasquez, director of the Tribunal de Mineria, travelled over the greater part of New Spain; and he traced on the map which

we have already cited the branches of the Sierra Madre de Anahuac, the eastern branch which runs from Zimapan towards Charcas and Monterey, in the small kingdom of Leon, and the western branch which extends from Bolaños to the Presidio de Fronteras. The manuscript memoirs of M. Sonnenschmidt, a learned Saxon mineralogist, who visited the mines of Guanaxuato, Zacatecas, Chihuahua and Catorce, and the labours of M. del Rio, professor in the school for mines of Mexico, and of Don Vincente Valencia, residing at Zacatecas, have also furnished me with very useful information. I owe much also to the celebrated D'Elhuyar at Mexico ; M. Chovell at Villalpando; M. Abad at Valladolid; M. Anza at Tasco; Colonel Obregon at Catorce; and a great number of rich proprietors of mines and religious missionaries, who were so good as to take an interest in my work. Notwithstanding all the pains I took to be informed as to the direction of the chains of mountains, I am far from regarding this part of my work as perfect. Occupied these twenty years in examining mountains and collecting materials for a geological atlas, I well know how hazardous an undertaking it is to trace the mountains on an ex. tent of territory of 118,000 square leagues.

I could have wished to draw up on a large scale two maps of New Spain, the one physical, the other purely geographical ; but I was afraid of rendering the work too voluminous. The hatch

Hence the geogra

ings which designate the slope and undulation of the ground, afford at the same time a shade to the maps overcharged with names.

These names become not unfrequently illegible, when an engraver attempts to produce a grand effect by the distribution of chiaro scuro. pher who has carefully discussed the astronomical position of the places becomes uncertain whether he ought to preserve distinctness of character, or render more perceptible the relative height of mountains. One of the most beautiful maps which was ever published in France*, the one drawn up in the war depôt in 1804, sufficiently proves how difficult it is to reconcile two opposite inte. rests, the interest of the geologist and that of the astronomer. The fear of giving too great an extent to my work, and the difficulties attending the publication of an atlas of which no government defrays the expense, made me abandon a project which I had once formed of joining to each section of territory a physical map in a horizontal projection.

* We have discussed in the eighth chapter the extraordinary regularity in the position of the Mexican volcanoes. I am uncertain as to the longitude of the Pic de l ancitaro, which has been twice surveyed from a distance. I fear some error bas crept in at copying the angles; but the latitude of this Pic is sure enough to within about eight minutes.

II. MAP OF NEW SPAIN AND THE CONTER. MINOUS COUNTRIES ON THE NORTH AND EAST.

I have already explained the motives by which I was induced to curtail my large map of New Spain within too narrow limits for representing, on the same plate, tlie-whole extent of the kingdom from New California to the intendancy of Merida. The second map is destined to remedy this inconvenience. It shows at once, not only all the provinces which depend on the viceroy of Mexico and the two commandants of the provincias internas, but also the island of Cuba, whose capital may be considered as the military port of New Spain, Louisiana, and the Atlantic part of the United States. This map was drawn up by M. Poirson, an able engineer of Paris, from materials furnished to him by M. Oltmanns and me. It embraces the immense extent comprehended between the 15° and 42° of latitude, and the 750 and 130° of longitude. At first I meant to extend this map to the south as far as the mouth of the Rio San Juan, for the sake of indi. cating different canals, of which the construction was proposed to the court of Madrid, and which would serve to establish the communication between the two seas, to be discussed in the second

chapter of this work. But on perceiving that the peninsula of Yucatan, and the coast of Monterey, would not be represented with the developement which they deserved, I chose rather to preserve a larger scale, and to extend my map no farther south than the gulf of Honduras.

The principal part, that which comprehends the kingdom of New Spain, is a faithful

copy

of my large map,

of which I have given an analysis. The Yicatan was added from the map of the gulf of Mexico, published by the Deposito Hydrografico of Madrid. New California was taken from the atlas which accompanies the account of the voyage of the corvettes Sutil and Mexicana, and from a memoir of M. Espinosa, printed in 1806, entitled, Memoria sobre las observaciones astronomicas

que

han servido de fundamento a las cartas de la costa N. O. de America, publicadas por

la direccion de trabajos hidrograficos. When this memoir gave different results from those contained in the Relacion del viage a Fuca, they were preferred as founded on more solid bases *. The

* I have placed Monterey in latitude 36° 35' 45", and longitude 124° 12' 23", and Cape S. Lucas in latitude 22° 52' 33", longitude 112° 14' 30". The longitude of Monterey which I have definitively adopted with M. Espinosa, differs less from that of Vancouver than the result published by M. Antillon. The difference between the opinion of the Spanish navigator and that of the English navigator is only an arc of 18' as already stated. (Here it is of importance to observe, that the commencement of this geographical introduction,

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