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Acapulco is, according to my chronometer, 2'54" of time. Now Mexico, having been found by the medium of my lunar distances 6b 45' 42* of longitude, there would result for Acapulco, excluding every other species of observation, 6h 48' 48". An uncertainty of 19" of time is very trifling for the comparison of two longitudes, deduced from simple distances from the moon to the sun. I found Acapulco in 1803, by the lunar tables of Mason, 102° 8' 9".
This position differs very little from what is indicated by the atlas which accompanies the voyage of the Spanish navigators to the Straits of Fuca, and which is 102° 0' 30' of longitude, and l6°50' Cf of latitude. This atlas is founded on the operations of the expedition of Malaspina. However M. Antillon, in an excellent memoir above cited, gives a result, deduced from the same operations, which differs more than a third of a degree. He asserts, that the observations in 1791, by the astronomers who embarked in the corvettes laDescuberta and la Atrevida, fixed Acapulco at 102° 21' 0" of longitude; a result which appears to me less exact, though more conformable to the manuscripts left by these navigators in Mexico. They themselves deduced, from eight series of lunar distances, 102° 26'; from an immersion of the first satellite, 102° 20'40"; and from the transference of time* from Guajaquil, 102° 22' 0"; an admirable, but perhaps merely apparent, harmony, on account of the errors of the old lunar tables. Besides, the longitude, deduced in 1794 from the operations on board the brigantine Activo, was equally western. This expedition examined the coasts of Sonzonate and Soconusco, and fixed the longitude of Acapulco at 102° 25' 30"; though I am completely ignorant of the nature of the observations on which this longitude is founded.
* This chronometrical longitude of 102° 22' is also found in the minute plan of the port of Acapulco, drawn up by the expedition of Malaspina, and copied at the audience of the pilotage of Lima. It appears, iri fact, that the astronomers of this expedition had at first adopted much morewestern positions than those afterwards adopted by the Deposito Hydrografico of Madrid. The difference for Acapulco is 20', for Guayaquil l&, for Panama and Realexo 18', en arc.
A note in the hand-writing of one of the astronomers of the expedition of Malaspina, left at Mexico, bears, that they thought themselves warranted to deduce, from some eclipses of satellites observed, at the same time, at the capital and Aca» pulco, a difference of meridians of 2' 2 ln in time. In placing, with the new maps of the Deposito HydrogrqficO, Acapulco at 102* O', we should find Mexico 101° 24' 45", which is, to within about 700 toises,the longitude given by the medium of all my operations. I should doubt, however, of the accuracy with which the distance from the capital to Acapulco was deduced. It is probably greater than 2' 21", though perhaps also somewhat less than the 2' 54ff given by my chronometer, worn out with five years travelling, and passing rapidly in so mountainous a region from the extreme heats of the coast, to the frosts of Guchilaque; that is to say, from a temperature of 36° to another of 5* of the centigrade thermometer.
Formerly Acapulco was placed four degrees further to the west in the South sea. Jean Covens and Corneille Mortier,in their map of the Mexican archipelago, make the longitude of Acapulco 106° 10' 0"■ The old maps of the depot of the marine make it 104° 0'. This longitude became gradually more eastern. Bonne, in the geographical memoir annexed to the work of Raynal, gives 103* O': Arrowsmith in 1803 makes it 102° 44'.
The Knowledge of the Times (Connoissance des Temps) for the year 1808, fixes Acapulco very well in point of longitude (102° 19' 30'), but assigns it a latitude too southern by lO. This error is so much the more striking, as, before the expedition of Malaspina, this port was placed at 17° 20', or 17° 30', as is proved by the maps of d'Anville and those of the marine depot. However, Covens makes the latitude 16° 7, while in 1540 the pilot Domingo de Castillo gives it at 17° 25'. In the time of Herman Cortez, the capital of Mexico was believed to be three degrees to the west of Acapulto, almost north to south with the port de los Angeles. Probably the maps which the Mexicans themselves had constructed of their coasts, and which the emperor Montezuma presented to the Spaniards, had an influence on this position. I have myself remarked among the hieroglyphic manuscripts in the collection of Boturini, preserved in the palace of the viceroy of Mexico, a very curious plan of the environs of the capital. I should add, that long before the observations of the expedition of Malaspina at Acapulco, those who were employed in astronomy at Mexico admitted, as certain, that the capital and port were in the same meridian.
JOURNEY FROM MEXICO TO ACA-
Having fixed the position of the three principal places of the kingdom, let us examine the two roads which lead from the capital to the South sea, and to the Atlantic ocean. The first may be named the Asiatic road, and the other the European ; as these denominations designate the direction of the maritime commerce of New Spain. I determined, on these highly frequented roads, seventeen points either in latitude or longitude.
Village of Mescala.—I found its latitude, by the culmination of Antares, 17° 56' 4", and the longitude, by the chronometer, 6h 47' 16//, supposing Acapulco 6h 48' C2A". Tfie city of Chilpanzingo, from angles taken at Mescala, appears to be 17° 36' of latitude, and 6h 46' 53" of longitude.
Venta de Estola, a solitary house in the midst of a wood near a fine spring. I took several altitudes of the sun there: the chronometer gave 6h 46' 56' of longitude.
The village of Tepecuacuilco.—Latitude found by the method of Douwes, uncertain to the extent of nearly 3', 18' 20° 0".
Village of Tehuilotepec.—Longitude, 6h 47* 12#. Double altitudes of the sun gave me 18° 35' 0"; but this latitude, determined under unfavourable circumstances, is uncertain from six to seven minutes. The position of this place is interest-1 0 ing, on account of the proximity of the great mines of Tasco.
Pont d'lstla, in the great plains of S. Gabriel.' I found it 18° 37 41/y of latitude, and 6h 4& 19" of longitude.
Village of San Augustin de las Cuesas.'—Longitude, 6h 45' 46". Latitude, 19° 18'37". This village terminates on the west the great valley of Mexico.
It will be useful, for a minute acquaintance with the country, to add the distances which the natives, particularly the muleteers, who travel as it were in caravans to the great fair of Acapulco, reckon from one village to another. The true distance from the capital to the port being known, and supposing a thirtUmore for windings in a road both strait and of easy access, we shall find the value of the leagues in use in these countries. This