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I should have given the preference to Murdoch's, which deserves to be generally followed. The scale of my map is 32 millimetres * for every degree of the equator. The scale of increasing latitudes is not founded on the tables of Don Jorge Juan, but on those which M. de Mendoza calculated for the spheroid.
To give a more suitable form to the map of Mexico, the scale was only extended from the 15° to the 41° of north latitude, and from the 96° to the 117° of longitude. These limits did not admit of giving in the same map the intendancy of Merida o/ the peninsula of Yucatan, which belongs to the kingdom of New Spain. To include in the map the most eastern point, which is Cape Catoche, or rather the island Cozumel, seven additional degrees of longitude are requisite,'which would have forced me to comprize in the same map a portion of the kingdom of Guatimala, for which I have no data, all Louisiana, all western Florida, a part of the Tennessee, and of the Ohio.
It is in vain to seek, in this general map of New Spain, the Spanish establishments on the northwest coast of America, establishments which are insulated, and may be considered as colonies dependant on the metropolis of Mexico. To exhibit in the same map the missions of New California would have required an additional eightdegrees of longitude; for the most northern point of the kingdom is the presidio of San Francisco, situated, according to Vancouver, in 87° 48' 30" of north latitude, and 124° 27' 45" of west longitude. Hence a map of New Spain, to deserve the name of a general map, should embrace the immense countries included within the 89° and 125° of longitude, and within the 15° and 38° of latitude. To avoid the inconvenience of representing on a large scale countries which, in a political view, possess by no means the same interest, I wished to compress my labour within narrower bounds. I drew up, in a much smaller form, a second map, which not only exhibits in a coup d'ceil all the territories which depend on the viceroyalty of Mexico, but which may also be consulted by those who wish to examine the different communications projected between the Atlantic ocean and the South sea. The motives which have occasioned this latter map to be extended to the port of Philadelphia, and even to the mouth of the Rio San Juan at Choco, will be explained in the sequel of this work.
* 1.25987 In. English. Trans. VOL. I. C
Although, according to the principles often laid down by me, I persist in preferring the new measures to the old, I have not however added to my maps the scale of centesimal degrees. The Bureau of Longitudes having constantly followed, both in the Knowledge of Times (Connoissance ties Temps) and in the new Astronomical Tables lately published, the old manner of computing the latitudes, a single individual would in vain oppose the torrent, in publishing latitudes expressed in centesimal parts. It is to be hoped, however, that the introduction of the metrical system, fixed by the arrete of the 13 Brumaire, year IX, will become gradually general. The degrees of longitude which I indicate are computed to the west of the meridian of the Imperial Observatory at Paris. If the great body of the public were not averse to even the most useful innovations, I should have preferred, to the meridian of Paris, the universal meridian proposed by one of the first geometricians of the age*, founded on the movement of the great axis of the solar ellipsis. This universal meridian is 185° 30" to the east of Paris, which is 166° 46' 12" of the ancient sexagesimal division. It passes, consequently, by the South Sea, 12' to the east of the isle of Erromanga, which belongs to the archipelago of the Holy Ghost (du Saint Esprit). . The introduction of a universal meridian, founded on nature itself, which would not shock the national vanity of Europeans, is so much the more to be desired, that we every day see augmented the number of first meridians arbitrarily traced on maps. Spain, for several years back, reckons five: Cadiz, the most in use with navigators; Carthagena; the new observatory at the isle of Leon; the college of Nobles at Madrid, introduced by the beautiful maps of M. Antillon; and the point de la Galera at the island of Trinidad. To these five meridians might be added other two which pass through the Spanish possessions, and have been adopted by a great number of geographers: I mean the meridian of Teneriffe and of the island of Fer. The latter occasions inevitable confusion, d'Anville placing it between the town of Per and Cape West. So that there are seven first meridians, without reckoning Toledo, in the sole dominions of the king of Spain.
I have followed, in the denomination of the seas which wash the coasts of Mexico, the ideas proposed by M. Fleurieu in his observations on the hydrographical division of the globe; a work in which the most enlarged views are united to a profound historical erudition. The Spanish names have often been added to facilitate the reading of travels written in Spanish.
In drawing up the map of Mexico, I began by assembling together all the points fixed by astronomical observations,from which I formed a view, which, for the better appretiating the degree of confidence which the results deserve, indicates the nature of the observation and the name of the observer. The number of these points amounts to 74, of which 50 are situated in the interior of the country. Of this latter class there were only fifteen known before my arrival at Mexico in the month of April, 1803. It may be useful to discuss some of the thirty-three points whose position is determined by my own observations, and which are all comprised between the 16° 50' and 20° 0' of latitude, and the 98° 29' and 103° 12' of longitude. -While we are fixing these positions, we shall enter into some historical details respecting the extraordinary errors which have been propagated to this day in the most recent and current maps.
Several meridian altitudes of the sun and stars gave me for the latitude of the capital at the convent of St. Augustin*, 9° 25' 45". The longitude deduced from the eclipses of the satellites of Jupiter, from the distances from the moon to the sun, from transference of the time from Acapulco, and from a trigonometrical operation for estimating the difference of meridians between Mexico and the port of Vera Cruz, is 6h 45' 42" or 101° 25' 30". I shall observe once for all, that I rely on the numbers which result from the very careful calculations of M. Oltmanns, a distin
* The great gate of the cathedral church of Mexico is 12'' farther north, and 108 farther east, than the convent of St. Augustin, near which I made my observations.