Page images

Latitude of Toluca by a de la Grue 19° lô 04", by Fomahant, 19° 16' 3". I endeavoured as much as possible constantly to observe the same stars to diminish any error from the uncertainty of the declination.

The position of Nevado de Toluca, the latitude of Patequero, a city situated on the banks of the lake of the same name, of Salamanca, St. Juan del Rio, and Tisayuca, are founded on imperfect observations. There are circumstances in which the method of Douwes gives very inaccurate results; but in a country presenting so few fixed points we must often be contented with a simple approximation. I think I can venture to assert, that the longitudes of Queretaro, Salamanca, and San Juan del Rio, may be confidently relied on.

Even in the valley of Mexico there are several very important points, the position of which was determined by Velasquez, the celebrated Mexican geometrician of the eighteenth century. This indefatigable man executed in 1773 an extensive survey along with a trigonometrical operation, to prove that the waters of the lake of Tezcuco might be conducted to the canal of Huehuetoca. M. Oteiza was kind enough to calculate for me the triangles of Velasquez, of which I possess the manuscripts. M. Oltmanns went over the same calculations. He subjected the positions of the signals to the latitude and longitude which we have here adopted for the convent of St. Augustin in

VOL. 1.


the capital of Mexico. These results of M. Olemanns are contained in the table of geographical positions. No doubt can remain "s to the oblique distances; but the want of observations of azimuths gives a little uncertainty to the reduction of the perpendiculars or differences in latitude and longitude. We shall return to this subject in the analysis of the map of the environs of Mexico.

The seventeen positions fixed by M. Ferrer in the environs of Vera Cruz depend on the longitude of that port. That longitude having been supposed by me 10° 45' farther west than the Spanish astronomer indicates, I have reduceri to the meridian of Paris the longitudes published by M. Fe rer, adding 8° 47' 15" ; for that observer calculated the lunar distances, from the knowledge of Times, at an epoqua when Cadiz was believed to lie 8° 36' 30% to the west of Paris. I have for the same reason changed the absolute longitudes of Xalappa, the Cofre de Perotte, and the Pic d'Orizaba. M. Ferrer, for instance, places the latter at 90° 48' 23" of west longitude from Cadiz, while from the same meridian he fixes Vera Cruz at 89° 41' 45'.



The north-west part of New Spain, the coast of California, and of what the English call New Albion, contain many points determined by the

most exact geodesical and astronomical operations of Quadra, Galeano, and Vancouver. Few European charts are better established than those of Western America, from Cape Mendocino to Queen Char. lotte's Straits.

Cortez, after setting on foot two voyages of discovery in 1532, under Diego Hurtado de Men. doza, Diego Becerra, and Hernando de Griscalva, examined himself in 1593 the coast of California, and the gulf which has since very justly borne the name of the sea of Cortez*. In 1542 the intrepid Juan Rodriguez Cobrillo pushed as far north as 44° of latitude; the Sandwich Islands were discovered by Juan Gaëtan; and in 1582 Fran. cisco Gali discovered the north-west coast of America under 57° 30' of latitude; so that long before the intrepid Cook made this part of the great ocean to be known, which cost him his life, the same regions had been visited by Spanish navigators. But very often the rapid promulgation of discoveries does not depend upon him who makes them. Yet the merit of a private citizen is independent of the false policy of a government, which from an ignorance of its own interest would prevent a nation from enjoying the glory which it has earned. But this subject, equally delicate and interesting, has been treated with great discern. ment, in the historical introduction to the voyage

* Gomara Hist. cap. 12.


of Marchand, and in the introduction to the account of the Spanish expeditions undertaken for the discovery of the Straits of Fuca.

The observation of the transit of Venus in 1769, occasioned the voyage of MM. Chappe, Doz, and Velasquez, three astronomers, of whom the first was a Frenchman, the second a Spaniard, and the third a Mexican, and, what is more, the pupil of a very intelligent Indian of the village of Xaltocan. Before, however, the arrival of these astronomers in California, the true latitudes of Cape San Lucas and the mission of St. Rose had already been found by Don Miguel Costanzo, at present general of brigade and head of the corps of engineers. This respectable officer, who displays the greatest zeal for the geography of the country, found by gnomons and English octants of a very perfect construction, San Jose to be 23° 2' 0"; and Cape San Lucas, 22° 48' 10". Till then it was believed, as is proved by the chart of Alzate, that San Jose lay in 22° 0' of latitude.

The detail of the observations of the Abbé Chappe does not inspire much confidence. Provided with a large quadrant of three feet radius, Chappe found the latitude of San Jose by Arcturus 23° 4' 1"; by Antares, 23° 3' 12". The medium of all the stellar observations differs from the result of the passages of the sun through the meridian by 31". There are some of the solar observations which differ from one another l' 19'. M. Cas. sini, however, calls them “ very exact and very accordant*". I cite these examples, not for the sake of discrediting astronomers who have so many titles to our esteem, but to prove that a sextant of five inches radius would have been more useful to the Abbé Chappe than his quadrant of three feet radius, difficult both to place and to verify. Don Vicente Doz placed San Jose at 23° 5' 15" latitude. The longitude of this celebrated village in the annals of astronomy was deduced from the transit of Venus, and from the eclipses of Jupiter's satellites, observed by Chappe, and compared with the tables of Wargentin. M. Cassini fixed it by a medium at gh 2810", or 112° 2' 30". Father Hell adopted 7h 37' 57" for San Jose. The longitude which results from Chappe's observations is 30 12' farther east than the one adopted in 1768 in the map of Alzatef. M. Velasquez too, the Mexican astronomer, constructed a small observatory in the village of St. Anne, where he observed by himself the transit of Venus, communicating the result of his observation to M. Chappe and Don Vicente Doz. This result, published by M. de Cassini, agrees very well with the manuscript observations which I procured at Mexico, and might


* Voyage en Californie, p. 106.

+ Nouvelle Carte de l'Amérique Septentrionale, dediée à l'Académie Royale des Sciences de Paris par Don Joseph Antoine de Alzate et Ramiret, 1768.

« ՆախորդըՇարունակել »