Sa Sag SS ere SE eee aa 
= ~ Se 
SS, reer 
174 LAKE OF VALENCIA. 
feet thick in the heart of the country, as far as Tur- 
mero and La Concesion near Victoria. These facts 
prove a retreat of the waters ; but no evidence exists 
that any considerable diminution of them has taken 
place in recent times, although within the thirty 
years preceding Humboldt’s visit the gradual de- 
siccation of this great basin had excited general at- 
tention. This, however, is not dependent upon sub- 
terranean channels, as some suppose, but upon the 
effects of evaporation, increased by the changes ope- 
rated upon the surface of the country. Forests, by 
sheltering the soil from the direct action of the sun, 
diminish the waste of moisture ; consequently, when 
they are imprudently destroyed, the springs become 
less abundant, or are entirely dried up. Till the 
middle of the last century, the mountains that sur- 
round the valleys of Aragua were covered with 
woods, and the plains with thickets interspersed 
with large trees. As cultivation increased the syl- 
van vegetation suffered ; and as the evaporation in 
this district is excessively powerful, the little rivers 
were dried up in the lower portion of their course 
during a great part of the year. The land that sur- 
rounds the lake being quite flat and even, the de- 
crease of a few inches in the level of the water ex- 
posed a vast extent of ground, and as it retired the 
planters took possession of the new land. 
The idea that the lake will soon entirely disap- 
pear, Humboldt treats as chimerical, considering it 
probable that a period will shortly arrive when the 
supply of water by the rivers and the evaporation 
will balance each other. The mean depth is from 77 
to 96 feet, and there are some parts not less than 224 
or 256 feet. The length is thirty-four and a half 
