t 



543 



from the Rio Negro. I discern from it the same objects, as 

 I perceived from my former dwelling, near the Rio Manza- 

 nares. I see on the south the mountains of the Brigantine, 

 the Tataraqual, and the whole chain of the mountains of 

 New Andalusia ; on the north-west, the group of islands 

 lying between the ports of Cum ana and Nueva Barcelona, 

 the Caraccas Islands, Picuita, and Boracha. Distance of 

 these islands from ten to fifteen miles. Bird's quadrant with 

 a double division, carefully verified by a spirit level and 

 plumbline. The instrument is placed on a thick wall. I 

 constantly employed the division into 96° ; every degree of 

 which is equal to 56' 15". The vernier subdivides the de- 

 grees into 120 parts. The error of collimation was deter- 

 mined by the latitude of the place, and by comparison with 

 a sextant of Ramsden's. It amounts to 8' 40" (sexag. div.) 

 to be added to the zenith distances. The object-glass of the 

 quadrant is 124 feet 11 inches above the level of the sea. 

 In order to be more certain, that no accident influences the 

 angles of depression and of suspension, I measure every 

 time the angle of altitude of a tower (A), which from it's 

 elevation and proximity cannot be sensibly affected by the 

 changes in the horizontal refractions. 



" The first of September, 1800, at 23& 10', the points of 

 the islands, and capes of the neighbouring continent, all ap- 

 pear elevated, suspended. Dollond's telescope, magnifying 

 65 times. Therm, in the open air, in the shade, 22t»°R. ; 

 Deluc's hygrometer, 45 2° ; cyanometer, 20° ; A (or tower 

 serving as a rectification of the instrument), 94° 31' 3" ; B, 

 or eastern cape of the island of Caraccas, 95° 52' 25" ; C, 

 or summit of the small island Picuita, 95° 56' 30" 5 D, or 

 base of the island Picuita, 95° 58' 23" ; E, or height of 

 the island of Boracha, 95° 46' ; F, or depression of the ho - 

 rizon of the sea, 95° 58' 30". The sea water, 21*4° ; the 

 sand of the plains between the town and sea, 30*8° R. 



" The third of September, 19 h in the morning. Therm. 

 21° R. Hyg. 43°. Cyan. 14<>. 



