82 Professor Fournet’s Researches on the 
commence between the middle of September and the middle 
of October, and last five months. At Vallarica they are very 
heavy in January and February, and they vary according to 
the height ; on the banks of the San Francisco they cease in 
January. The vegetation follows the progress of these udo- 
metric and thermometric variations. The soil of Patagonia 
is extremely arid, and is covered with /andes analogous to 
those of Gascony ; towards the north, in the Pampas, there 
are meadows; still further to the north there are thick forests ; 
and, lastly, the rich intertropical vegetation is met with. Ac- 
cording to M. d’Orbigny, a portion of these results is to be 
attributed to the preponderance of the winds, which on that 
side of the Andes have a north and north-east direction, the 
reverse of their direction on the oceanic coast. We have still 
to examine the cause of this opposite parallelism of the at- 
mospheric currents of the two slopes of the Andes. 
On the Atlantic coast the distribution of rains is still more 
anomalous, as may be seen by the following details, derived 
from the observations of Dampier, Frezier, Piron, Vignal, 
Martius, Jacquemont, Saint Hilaire, and D’Orbigny. 
At Buenos Ayres and Montevideo (lat. 33° S.), the atmo- 
spherical variations are considerable ; the same is the case 
at Rio Janeiro (lat 23° S.), where there are no fixed epochs 
for the rains, although the most violent fall from October to 
March, whereas they are inconsiderable in June, July, and 
August. It results from this statement that the latter place 
may be included in the intertropical climate of the southern 
hemisphere ; regarding it, however, as complicated by an ac- . 
cidental circumstance which occurs as far as Olinda (lat. 8° 
S.). At Bahia (All Saints, lat. 18° S.) the rains fall from 
March or April to September, becoming torrential in the 
middle of summer, contrary to what should take place in the 
intertropical region of that hemisphere. Itis to be remarked, 
moreover, that the ordinary south-east winds only prevail on 
the east coasts during the rainy seasons, between March and 
September, after which they are replaced during the droughts 
by north-east winds, thus giving rise to a sort of monsoon. 
There is nothing less constant than the periodical return of 
the land and sea breezes; the sea breezes often prevail at 
