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Colombia between the Years 1820 and 1830. 5 
contiguous elevations which impede the circulation of air, and 
produce reflected heat. The various combinations of these cir- 
cumstances may be considered as affording a rule of the increase 
or diminution of temperature. Thus, La Guayra, situated ona 
sandy beach backed by a perpendicular wall of rocks, has no 
counterpoise to the excess of heat but the sea breeze, and the re- 
mote influence of the ridge of the Silla, which no where reaches 
the limit of perpetual snow. Humboldt considers it in conse- 
quence as the hottest place on the shores of the New World, 
(Personal Narrative, vol. iii, p. 386,) the mean annual tempera- 
ture being 82°-6; yet the observations I made during some 
months’ residence in Maracaybo give an annual mean of 84°63. 
Nor is this surprising, when we consider the localities of both 
places. In Maracaybo the sun’s rays are reflected from a barren 
sandy soil, scantily sprinkled with Mimosas and prickly plants. 
The mountain chains are too remote to have any influence on the 
atmosphere, so that several years frequently pass without any 
regular fall of rain. The vicinity of the lake, no doubt, acts 
slightly as a refrigerant; but the city is built on the border of 
its outlet to the sea, where it is both narrowest and shallowest, 
and is consequently heated nearly to the temperature of the in- 
cumbent atmosphere. Add to this, the small sandy elevations to 
the north, which intercept the partial effect of the sea-breezes, so 
that they are scarcely felt, except in the months of December and 
January, when the thermometer sometimes sinks to 73°; yet the 
medium even of these two months is not less than 81°; while 
that of La Guayra from November to December at noon, is, ac- 
cording to Humboldt, 75°-8, and at night 70°-9. (Personal Nar- 
rative, vol. iii, p. 387.) Rio Hacha is situated on a sandy beach; 
the sea-breeze blows with such violence that boats can scarcely 
land between ten in the morning and four in the afternoon, 
These winds, however, sweeping over the hot plains of Coro and 
Maracaybo, have but a partial effect in lowering the temperature, 
the annual mean of which is 19-98 less than that of Maracaybo. 
I never saw the thermometer lower than 75°, nor above 89°, 
In Santa Marta the average of the coolest months is 829-25. The 
thermometer, however, never rose during my residence there 
above 87°. The soil is sandy, and the city is surrounded by 
bare rocky heights to the north and south, which counterpoise 
the cooling influence of the Sierra nevada, (snowy mountains, } 
