DtVlfESS Oif XUE Al’ilOSPUEliE. 
436 
west. The Academy of Sciences recommended the men of 
science who accompanied the unfortunate La Perouse, to 
employ small air-balloons for the purpose of ascertaining 
at sea the extent of the trade-winds within the tropics. 
Such experiments are very difficult. Small balloons do 
not :n general reach the height of the Silla; and the light 
clouds which are sometimes perceived at an elevation of 
three or four thousand toises, for instance, the fleecy clouds, 
called by the French moutons, remain almost fixed, or have 
such a slow motion, that it is impossible to judge of the 
direction of the wind. 
During the short space of time that the sky was serene 
at the zenith, I found the blue of the atmosphere sensibly 
deeper than on the coasts. It is probable that, in the 
months of Jidy and August, the difference between the 
colour of the sky on the coasts and on the summit of the 
Silla is still more considerable, but the meteorological phe- 
nomenon with which M. Bonpland and myself were most 
struck during the hour we passed on the mountain, was 
the apparent dryness of the air, which seemed to increase 
as the fog augmented. 
This fog soon became so dense that it would have been 
imprudent to remain longer on the edge of a precipice of 
seven or eight thousand feet deep.* We descended the 
eastern dome of the Silla, and gathered in our descent a 
gramen, which not only forms a new and very remarkable 
genus, but which, to our great astonishment, we found again 
some time after on the summit of the volcano of Pichincha, 
at the distance of four hundred leagues from the Silla, in the 
southern hemisphere.f The Lichen floridus, so common 
in the north of Europe, covered the branches of the befaria 
and the Gualtheria odorata, descending even to the roots 
of these shrubs. Examining the mosses which cover the 
rocks of gneiss in the valley between the two peaks, I was 
surprised at finding real pebbles, — rounded fragments of 
* In the direction of north-west the slopes appear more accessible; and 
I have been told of a path frequented by smugglers, which leads to Cara- 
valleda, between the two peaks of the Silla. From the eastern peak I took 
the bearings of the western peak, 64° 40' S.W.; and of the houses, which 
I was told belonged to Caravalleda, 55° 20' N.\V\ 
f Aegopogon cenchroides. 
