BBT ATI) BAIITT SEASOXS. 
223 
than is supposed by the inhabitants of Curnana, on account 
of their exaggerated ideas of the cold of Cumanacoa. But 
the difference of climate observable between places so near 
each other is perhaps less owing to comparative height than 
to local circumstances. Among these causes we may cite the 
proximity of the forests ; the frequency of descending cur- 
rents, so common in these valleys, closed on every side ; the 
abundance of rain; and those' thick fogs which diminish 
during a great part of the year the direct action of the solar 
rays.. The decrement of "the heat being nearly the same 
within the tropics, and during the summer under the tem- 
perate zone, the small difference of level of one hundred 
toises should produce only a change in the mean temperature 
of 1° or T5°. But we shall soon find that at Cumanacoa the 
difference rises to more than four degrees. This coolness of 
the climate is sometimes the more surprising, as very great 
heat is felt at Carthago (in the province of Popayan) ; at 
Tomependa, on the bank of the river Amazon, and in the 
valleys of Aragua, to the west of Caracas ; though the abso- 
lute height of these different places is between 200 and 480 
toises. In plains as well as on mountains the isothermal lines 
(lines of similar heat) are not constantly parallel to the 
equator, or the surface of the globe. It is the grand problem 
of meteorology to determine the inflections of these hues, 
and to discover, amid modifications produced by local causes, 
the constant laws of the distribution of heat. 
The port of Curnana is only seven nautical leagues from 
Cumanacoa. It scarcely ever rains in the first-mentioned 
place, while in the latter there are seven months of wintry 
weather. At Cumanacoa, the dry season begins at the 
winter solstice, and lasts till the vernal equinox. Light 
showers are frequent in the months of April, May, and June. 
The dry weather then returns again, and lasts from the sum- 
mer solstice to the end of August. Then come the real 
winter rains, which cease only in the month of November, 
and during which torrents of water pour down from the 
skies. 
It was during the winter season that we took up our first 
abode in the Missions. Every night a thick fog covered the 
sky, and it was only at intervals that I succeeded in taking 
some observations of the stars. The thermometer kept from 
