78 Professor Fournet’s Researches on the 
validate the generality of the distribution of deserts on the 
Peruvian coasts ; these only cease with a return of the rains 
towards the impassable forests of Choco, to which succeeds 
the inter-tropical richness of the isthmus of Panama, and of 
the coast of Mexico, succeeded, in its turn, by beautiful 
cacti, and other fine plants of the rocks of California; after 
which, near the mouth of the Rio-Colorado, there occurs a 
European flora, developed under the influence of a tempera- 
ture comparable to that of Valencia and of Italy. 
The sub-tropical rainless zone presents, on the Peruvian 
coast, an immense development in length, as it comprehends 
about 20° of latitude—an anomaly which, according to 
Dampier, also extends into the sea for a distance of two or 
three hundred leagues. This exceptional phenomenon seems 
to depend on various causes. In the frst place, this coast 
is subjected to the almost permanent influence of the south- 
west and south (Peruvian mistral) winds, which being essen- 
tially cold, because they come from the South Pole, are not 
capable of carrying with them a large proportion of watery 
vapour from the sea which they traverse ; and, moreover, they 
pass from an icy temperature into warmer and warmer zones, 
so that they cannot precipitate their humidity. 
In the second place, this coast is washed by a marine cur- 
rent, which, proceeding from the South Pole towards the 
equator, brings with it a large quantity of cold water, and is, 
consequently, incapable of producing an abundant evapora- 
tion. This fact is likewise demonstrated by the observations 
of M. Duperrey, who found that at the port of Lima the tem- 
peratures of the sea are lower than those of the land, con- 
trary to what takes place in 12° of south latitude, where 
there is generally little difference between them. 
The immediate neighbourhood of the Andes must also pro- 
duce during the day ascending breezes, whose action corres- 
ponding to that of the ordinary south-west winds, rapidly 
collects vapours from their summits, thus producing the 
variable climates of Cusco, of Puno, and of La Paz. 
Lastly, The clouds driven to the opposite side by the south- 
east trade-wind, or by the north-east wind which most fre- 
quently prevails there, discharge themselves on the Cordil- 
