Note 130 — THE PLATEAU, OR TABLE-LAND, OF CAXAMARCA, THE ANCIENT CAPITAL OF THE INCA ATAHUALLPA, AND THE FIRST VIEW OF THE PACIFIC OCEAN, From the Ridge of the Andes.

p. 420—“Of importance in determining the longitude of Lima.”

At the time of my expedition the longitude of Lima, 436as determined by Malaspina and marked in the maps published by the Deposito Hidrografico de Madrid, was 5^h 16′ 53″. The transit of Mercury over the Sun’s disc, on the 9th of November, 1802 (which I observed at Callao, the port of Lima, from the Round Tower of the Fort of San Felipe), gave for Callao, by the mean of the contact of both limbs, 5^h 18′ 16″ 5; by the external contact only, 5^h 18′ 18″ (79° 34′ 30″). This result, obtained from the transit of Mercury, has been confirmed by Lartigue and Duperrey; and by observations made during Capt. Fitzroy’s expeditions of the “Adventurer” and the “Beagle.” Lartigue fixed the longitude of Callao at 5^h 17′ 58″; Duperrey made it 5^h 18′ 16″; and Capt. Fitzroy 5^h 18′ 15″. After having calculated the longitudinal difference between Callao and the Convent of San Juan de Dios at Lima, by carrying chronometers from the one place to the other during four journeys, I found that the observations of the transit of Mercury determined the longitude of Lima to be 5^h 17′ 51″ (79° 27′ 45″ W. from Paris, or 77° 6′ 3″ W. from Greenwich.) See my Recueil d’observations astron., vol. ii. p. 397, and Relation hist., t. iii. p. 592.