Colombia between the Years 1820 and 1830. 7 



San Francisco indicates the line of separation betwixt two dis- 

 tinct climates. It will be seen by the map, that from P. Galera 

 the coast, after running nearly due west, turns abruptly to the 

 south. 



2. On penetrating into the interior of the country, and exam- 

 ining the temperature of small elevations, we may take, as form- 

 ing an aggregate specimen of the whole country : 1. The damp 

 wooded valleys of the Orinoco and Magdalena ; 2. The forests 

 which border on the Pacific ; and 3. The immense plains of Ven- 

 ezuela, alternately flooded and parched with excessive heat. 

 Humboldt assigns to the valley of the Orinoco a mean tempera- 

 ture of 78° -2. The small number of observations I have made 

 on that of the Magdalena, would give a mean of nearly 83°, 

 which I should scarcely think too high, considering the localities 

 of the river, which, flowing from south to north, aff'ords no chan- 

 nel to the sea-breezes. Its mass of water is also much less con- 

 siderable than that of the Orinoco ; while its numerous sinuosities, 

 and the low ridges which border it in the upper part of its course, 

 contribute to render the air stagnant and suffocating. The tem- 

 perature of Honda, at 1,200 feet of elevation, is as high as that of 

 any part of the coast except Maracaybo. The unbroken forests 

 which extend from the roots of the duitenian Andes to the shores 

 of the Pacific have a much lower temperature, caused by the 

 proximity of the snow-capped Cordillera, and the humidity which 

 prevails throughout the year. Accurate observations give an 

 annual mean of 76°-78, or l°-42 lower than the valley of the 

 Orinoco, and 6°-22 lower than that of the Magdalena. The 

 mean temperature of the plains of Venezuela is reckoned by 

 Humboldt at 88-4, [L)e Distributione Geog. Plant, p. 92. ;) yet 

 several reasons may induce the belief that this calculation is ex- 

 cessive. This illustrious traveller performed his journey during 

 the summer season, when the atmosphere is heated by the rever- 

 berations from a parched and naked soil. Persons who have re- 

 sided near the Apure, state the climate in rainy weather to be 

 cool, and refreshed by a constant breeze. It is only on the coast 

 of the Pacific that the rainy season is the period of the greatest 

 heat, when the air is still, and undisturbed by those electric ex- 

 plosions so common on the mountains and in the interior. The 

 observations I made at Varinas and San Carlos, towards the be- 

 ginning of the winter season, give a mean of 81° ; and averaging 



