M. Bonne* justly complains of the want of agreement among the astronomical observations at Vera Cruz. After a long discussion he fixes on 99° 37'. This is nearly the same longitude which d'Anville and the French Neptune adopted, and it is that to which the English astronomers have long given the preference. The tables of Hamilton Moore indicate 99° 49′ 47′′; but Arrowsinith (map of the Spanish possessions, 1803) makes it 98° 40′, and nine years before, Mr. Thomas Jeffreys, geographer to the king of England, 100° 23′ 47′′.

If formerly the prevailing error was the assigning too great western longitudes to the American ports, the Abbé Chappe fell into the contrary extreme he deduced from his chronometer the longitude of 97° 18′ 15′′†. If this observer, who possessed more zeal than accuracy, could have taken the distances from the moon to the sun, he would have perceived the error of more than a degree, into which he had been induced by an excess of confidence in his chronometer.

The oldest astronomical observation at Vera Cruz (at the chateau St. Juan de Ulua) is undoubtedly that of the moon's eclipse in 1577. Comparing the end of that eclipse with a corresponding observation at Madrid, M. Oltmanns

* Atlas pour l'ouvrage de l'Abbé Raynal, p. 11. + Voyage en Californie, p. 102.

found a difference of meridians of 6h 26', and consequently the longitude for Vera Cruz of 102° 30'*.

The Abbé Chappe found the latitude 19° 9′ 38′′t, a position too southern by three minutes. I examined the small quadrant of Chappe which remains at Mexico, in the hands of Father Pichardo; and I am by no means astonished, that, with so imperfect an instrument, his observations were so inaccurate. Other geographers formerly placed Vera Cruz 20′ too far to the south. The map of New Spain of Alzate indicates even a latitude of 18° 50′ 0′′.

ACAPULCO.

This port, the finest of all those on the coast of the great ocean, lies according to my observations (at the house of the contador Don Baltasar Alvarez Ordoño) in 16° 50′ 29′′ of latitude, and 6" 48′ 24′′ =102° 6′ 0′′ of longitude. This position was deduced by M. Oltmanns from twenty-eight distances taken by me from the moon to the sun. Those of the 27th March, 1803, calculated according to the tables of Bürg, gave 61 48′ 32′′; and those of the 28th March 6 48′ 21′′.

Thedifference of meridians between Mexico and

* Memoires de l'Academie pour l'année 1726. Voyage en Californie, p. 103.

Acapulco is, according to my chronometer, 2′ 54′′ of time. Now Mexico, having been found by the medium of my lunar distances 6 45′ 42′′ of longitude, there would result for Acapulco, excluding every other species of observation, 6 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 16° 50' O" 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 la Descuberta 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 ad

This chronometrical longitude of 102° 22' is also found

mirable, 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.

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 Acapulco, a difference of meridians of 2′ 21′′ in time. In placing, with the new maps of the Deposito Hydrografico, Acapulco at 102° 0', 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

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, in fact, that the astronomers of this expedition had at first adopted much more western positions than those afterwards adopted by the Deposito Hydrografico of Madrid. The difference for Acapulco is 20', for Guayaquil 16', for Panama and Realexo 18', en arc.

than the 2' 54" 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 10. 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 Acapulco, almost north to south with the port de los Angeles. Probably the maps which the Mexicans themselves had constructed