395 



Negro. I count the nights, because I watched 

 during the greater part of them, in the hope of 

 seizing the moment of the passage of some star 

 over the meridian. That I might have nothing 

 to reproach myself with, I kept the instruments 

 always ready for an observation. I could not 

 even obtain double altitudes, to calculate the 

 latitude by the method of Douwes. What a 

 contrast between two parts of the same zone ; 

 between the sky of Cumana, where the air is 

 constantly pure, as in Persia and Arabia, and 

 the sky of the Rio Negro, veiled like that of the 

 Feroe islands, without Sun, or Moon, or stars ! 

 I felt so much the more pain in leaving the fort 

 of San Carlos, as I could not then hope to 

 obtain near that spot a good observation for 

 the latitude*. I found the dip of the magnetic 

 needle 22*6° cent. div. The magnetic force was 

 expressed by two hundred and sixteen oscilla- 

 tions in ten minutes of time. As the magnetic 

 parallels rise to the westward, and as I found on 

 the back of the Cordilleras, between Santa Fe 

 de Bogota and Popayan, the same dips observed 



* Five altitudes of the Sun, taken the 8th of May, (all 

 that I could obtain,) gave me, according to the time-keeper, 

 69° 58' 39' for the longitude of San Carlos. The error 

 therefore of the map of La Cruz, and of those by whom it 

 has been copied, was nearly two degrees. All that part of 

 America was carried too far toward the east. (See my 

 Ohserv. Astr., vol. 1, p. 238.) 



