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M. Velasquez measured two bases, the one of 37021 Mexican varas in the plain, frequently inundated, which separates the village of San Christobal, and the hill of Chiconautla; and the other of 4474 varas on the causeway which leads from the capital to the sanctuary of S. Miguel de Guadalupe. The second base was even measured twice. In resolving successively the series of triangles according to these values, we shall find the dirt ct distance from the cross of the mountain of San Christobal to the crest (Creston) of the Loma de Chiconautla. One of the bases gives for this distance 14099 varas, another gives 14101. The third triangle and the three last have each an ohtuse angle, but in these same triangles an error of a minute in the sharpest angle would but produce a difference of three or four varas on the length of the sides. Hence this operation is very valuable for the topography of Tenochtitlan.
Particular signs indicate on my map the positions which are founded on the triangulation of M. Velasquez, and those which I detern ined as. tronomically. We have added the results of my measurements with the barometer, calculated according to the co-efficient of M. Ramond. To facilitate the use of the map to those who study the history of the conquest, I have placed the an. cient Mexican names, beside the names at present in use. I have endeavoured to be very exact in
the Azteque orthography, following only Mexican authors, and not the works of Solis, Robertson, Raynal and Pauw, who disfigure the names of cities and provinces, like those of the kings of Anahuac.
IV. MAP, EXHIBITING THE POINTS WHERE
This map was drawn up for the sake of offering to the eye of the reader in one view the nine points which present means of communication between the two oceans. It will serve to explain what I have said in the second chapter of the first book. I have represented in nine assembled sketches the points of separation between the Ounigigah and the Tacoutche-Tesse, and those between the Rio Colorado and the Rio del Norte; the isthmuses of Tehuantepec, Nicaragua, Panama, and Cupica; the river of Guallaga, and the gulf of S. George; and lastly, the ravin from the Raspadura to the Choco, by which, since 1988, boats have passed from the Pacific to the Atlantic Ocean. The most , interesting sketches are those of the small canal of derivation from the Raspadura and the isthmus of Tehuantepec. I have traced the course of the rivers Huasacualco (Guasacualco) and Chimalapa from materials which I found in the archives of the viceroyalty of Mexico, and particularly from
the plans of the engineers Don Miguel del Coral and Don Augustin Cramer, whom the viceroy Revillagigedo sent to the spot The distances were rectified by itineraries very recently drawn up since the indigo of Guatimala came to pass through the forest of Tarifa, which is a new road opened to the commerce of Vera Cruz.
V. PLAN OF THE PORT OF VERA CRUZ.
This work would undoubtedly appear incomplete, if it did not contain the plan of the port from which all the Mexican wealth flous into Europe. To this day Vera Cruz is the only port which can receive European vessels of war. The plan which I publish is an exact copy of the one drawn up in 1798 by M. Orta, captain of the port of Vera Cruz. I have diminished the scale by one half, and added a few notes on the longitude, winds, atmospheric tides, and on the quantity of rain which falls annually. The mere sight of this plan proves the difficulty of every military attack against a country, which on its eastern coast offers no other shelter to vessels than a dangerous anchorage among shallows.
The double lines drawn on the plan of the port, indicate the direction which vessels intending to anchor ought to follow. Whenever the pilot discovers the edifices of Vera Cruz, he should take care that the tower of the church of St. Francis
cover the tower of the cathedral. He will continue this route ull the salient angle of the bastion of S. Crispin appear behind the bastion of St. Peter. He should then tack to the larboard, placing the prow towards the Isle of Sacrifices. Buoys (palos de marca)have been placed on the shallow of la Gallega near the point of the Soldado, to avoid the two dangerous rocks, called Laxa de Fuera and de Dentro.
VI. PHYSICAL VIEW OF THE ORIENTAL DECLIVITY OF THE TABLE LAND OF ANAHUAC.
The horizontal projections known by the name of geographical maps, give but a very imperfect idea of the inequalities of surface and physiognomy of a country. The undulations of the surface (mouve. mens du terrain), the form of the mountains, their relative height, and the rapidity of the declivities, can only be completely represented in vertical sections. A map drawn up on the ingenious plan of M. Clerc* supplies to a certain degree the
* This learned geographical engineer, who presides over topography in the Ecole Polytechnique, possesses in an eminent manner the talent of representing the figure of a country. Nobody ever reflected more than he has done on the means of expressing undulations of surface, and a work which he means to publish on the construction of maps, and on the construction of relievus, will form an æra in the history of topography
place of a relievo ; and lines drawn on a plane which has but two dimensions may produce the same effect as a model in relievo, if the extent of ground represented is not too great, and if it is thoroughly known in all its parts. But the difficulties are almost insurmountable when the horizontal projection embraces a hilly country of a surface of several thousand square leagues.
In the most inhabited region of Europe, for example, in France, Germany, or England, the plains which are the seat of cultivation are only elevated, in general, a hundred*, or two hundred metrest above one another. Their absolute heights are too inconsiderable to have any sensible influence on the climatet. Hence an accurate knowledge of these elevations is much less interesting to the cultivator than to the naturalist; and hence also, in the maps of Europe, the geographers merely indicate the most elevated chains
* About 328 feet. Trans. + About 056 feet. Trans.
# The interior of Spain presents a very striking exception; the soil of the Castiles in the environs of Madrid being six hundred metres of absolute elevation (about 1960 feet). See my memoir on the configuration of the soil of Spain, inserted in the itinerary of M. Alexandre de Laborde, T. I. p. CXLVJI, CLVI. From the data contained in that memoir, the small geological map attached to the interesting Rapport sur l'importation des Merinos, par M. Poyféré de Céré, 1809, was drawn up. It is to be regretted, however, that this map was not drawn up in all its parts according to the same scale of elevation.